Canine Hip Dysplasia, Part I

By Susan Thorpe-Vargas Ph.D., John Cargill MA, MBA, MS.
Reprinted with permission.

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system known to exist now or in the future without permission in writing from the publisher.

Limits of Liability and Disclaimer of Warranty:
The authors and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising out of, the furnishing, performance, or use of the information and suggestions contained in this book.

By Susan Thorpe-Vargas Ph.D., John Cargill MA, MBA, MS.
(Reprinted with permission).

To understand this genetically transmitted disease, we must first understand the workings of the normal canine hip

This is the first in a series of articles addressing canine hip dysplasia. What follows is written from the perspective that the readers of the series are conscientious breeders who are the guardians of the genetic pools that constitute their breeds. While this series of articles will not replace a stack of veterinary medical texts, it is a relatively in-depth look at the whole problem of canine hip dysplasia. Furthermore, the series is designed to be retained as a reference. When you finish reading it you will have a sufficient background to make rational breeding choices and will be able to discuss the subject from an informed basis with your veterinarian. You may not like what you read, but you will be more competent to deal with the problem.

Hip dysplasia is one of the most controversial and widespread problems in the dog fancy. So many old-wives tales, anecdotes, misconceptions and even lies abound that one of the goals of this series of articles must be to lay things out to the reader as they are, supported with some scientific basis.

Let's start with a hypothetical scenario, but one which too many of us have faced:

He's major-pointed; he moves like a dream; that head piece may just be the best you have ever bred. In short, this boy typifies everything that is good about your breed and is the culmination of many years of hard work, hopes, tears, frustration and all the ups and downs, joys and heartaches common to the fancy. Now it is time to X-ray his hips so that you can not only use him in your breeding program, but advertise him at stud. This is one boy that is going to make it, and we are talking national specialty here.

Problem - the radiographic results come back with a diagnosis of canine hip dysplasia-severe. What should you do?

More among us than will admit have had this experience, and most of those who haven't have seen it happen to other breeders concentrating on similar bloodlines. Now back to our hypothetical scenario:

You never suspected a thing. The dog never appeared to be in pain and his gait was what won him his major points. You have invested time, money and your hopes on this animal, and it all has been for naught! Now is the time for hysteria and self-blame:

• What went wrong?
• Could this have been prevented?
• Was he not fed correctly?
• Was he kept on an improper surface while growing?
• What is this disease that keeps reappearing in the most conscientious of breeding programs, and which frustrates our attempts to eradicate it?

The first step in understanding canine hip dysplasia is to recognize it as not just one disease but many diseases, which together result in degenerative effects on the hip joint. An extremely complex disorder, hip dysplasia is now thought by some to be the most noticeable manifestation of a systemic condition that can affect not only the hip joints but also those of the elbow, shoulder and event the joints between the vertebrae ^[1]. Whatever else might result from the systemic conditions of this polygenic and multifactorial disease, hip dysplasia remains a common, usually painful and often debilitating disease. "Efforts by dog breeders and veterinarians to reduce the prevalence of the disorder have proven marginally effective." ^[2]

While there is much that we do not know we do know that canine hip dysplasia is a genetically transmitted disease. If you need to, or if you disagree at this point, please re-read that statement. We will be repeating it throughout this series of articles, and this concept is the basis for determination of fitness for breeding. The genetic concept of heritability is a complicating factor and is one reason why hip dysplasia remains so controversial. So often when you breed you get more than you see. Without resorting to too much math, heritability is equal to the statistical variance due to genetic influence divided by the sum of the statistical variance due to the genetic influence plus the variance due to the environmental influence. It is easier to comprehend the mathematical notation than the statement of the equation:

            Vgenetics
H2 =  ---------------------
       Vgenetics + Venvironment

H² = heritability index
V_genetics = variance due to genetics
V_environment = variance due to environmental influences

Thus, heritability is defined as an estimate of how much environmental factors play in the expression of the inherited genes. A high heritability index means that environmental considerations are not as important as genetic elements. The numerical value or heritability index is a function not only of breed type but of the population from which the data is extracted. "Studies of hip dysplasia genetics have indicated that the disease is polygenic and multifactorial, with estimates of heritability index in the range of 0.2 to 0.3" ^[3]

For instance, in a 1986 Swedish study, the heritability of hip dysplasia in German Shepherds was 0.40 in Sweden, but only 0.25 in the British Isles during the same time period. The difference between breeds may also reflect their levels of inbreeding. The more inbreeding, the lower the heritability index because inbreeding reduces the total genetic variability-that is, the gene pool is smaller. Inbreeding is not a bad word. It only becomes problematic when undesirable genetic traits are concentrated within the gene pool. By definition, every purebred dog of any given breed is highly inbred, or else it would look like a feral dog. We frequently hear that the problem with the American Kennel Club purebred dogs is that they are inbred. We should hope so, otherwise, we could never fix type to the point where there were discernible differences between breeds. On the other hand, we would hope that the concentrated gene pools for the various breeds would have been concentrated from stock exhibiting only desirable genetic traits. We would hope that our field, bench and obedience champions would be fit to contribute to the gene pool. Of course, we know that is not true, or there would be no purpose in writing this article. ^{[4], [5], [6]}

To further complicate matters is the fact that the pattern of inheritance indicates that more than one gene is involved. Hip dysplasia is polygenic (involves many different genes) and multifactorial (influenced by many non-genetic factors). This makes sense when you think of the complexity of the various structures involved. Every cell in the body, except for sex cells, carries two copies of each gene and each gene codes for a specific characteristic. One very simple example is eye color:

If the cell's two sets of genes for a specific characteristic are exactly alike, then the animal is homozygous for that characteristic.

If the two genes are different, i.e., heterozygous, then one copy of the genes could code for blue eyes and the other could code for brown eyes.

Let's complicate the matter even further. If the animal carries two different copies of the same gene for eye color, only one copy can be expressed in any given eye. Closer to home, in humans for example, a child born to parents heterozygous for eye color (both parents have a blue-eyed gene and brown-eyed gene) will have a one-in-four chance of having blue eyes. This is because the gene for blue eyes is recessive and both copies for that code for blue eyes must be present before that characteristic can be expressed. On the other hand, if the child has brown eyes, we don't know what type of genes for eye color he or she has. This is because the gene for brown eyes is dominant and is able to "mask" the physical expression of the blue-eyed gene. Alternatively, the child could have only the genes that code for brown eyes. It is beyond the scope of this article to address the various "odd" eye color combinations, but co-dominance and variable penetrance may be what we are dealing with in canine hip dysplasia.

What you have just read is an example of phenotype vs. Genotype. Phenotype is the physical expression of a genetic characteristic. Genotype is genetic composition of the organism. Using our eye-color example, the child with two different copies of the gene will express the brown-eyed phenotype, but his or her genotype will be heterozygous.

Let's add to the complexity once again. Co-dominance of genes is a situation where neither gene is dominant. A clear example illustrating the concept of genetic co-dominance is flower color. A snap dragon homozygous (both copies of color genes exactly alike) for white petals crossed with a snap dragon homozygous for red petals will produce a flower with pink petals, not a flower with either white or red petals or a mixture of red and white petals. Many researchers feel that hip dysplasia may be a mixture of dominant, recessive and co-dominant genes. Quite probably, this is one of the reasons why isolation of the causative genetic factors of canine hip dysplasia has been so elusive.

The concepts that you need to be clear on as we leave this mini-course on genetics are: heritability index; genetic and environmental variability; dominant vs. Recessive genes; homozygous vs. heterozygous; genetic co-dominance; and most importantly that hip dysplasia is genetically inheritable and is polygenic and multifactorial. In short, you can get it in your breeding program when you bred from animals that did not show it.

Before we can discuss an abnormal process (disease), we need to first understand the normal process. In this case, we must be able to answer the question, "What is a normal hip, what makes it normal, and how does it get that way?"

First, what is the hip? The hip joint is a main weight-bearing joint consisting principally of a ball and socket. This joint connects the pelvis to the lower extremities. The ball is on the end of the femur (thigh bone) and the socket (acetabulum) is part of the pelvis. Note from figure 1 how the femoral head fits into the acetabulum in the normal hip joint. This will be key to all our discussions from this point forth. A true ball-and-socket joint has three degrees of freedom, that is, it supports rotation about three different axes. The canine hip joint is unusual as a ball-and-socket joint in that it has a fourth degree of freedom. The femoral head may be displaced laterally from the acetabulum. While this is the genius of this joint, allowing the attached appendage a full range of motion, it can also create a problem if there becomes too much laxity in the joint. Note the fourth degree of freedom in Figure 2, which provides for the femoral head (ball) to move directly away from the acetabulum (socket). From Figures 1 and 2, it should be obvious that much lateral displacement of the femoral head from its seat in the acetabulum will produce high joint stresses during weight bearing. This joint laxity will be a major consideration for the changes it causes in the joint mechanics as we progress through this series of articles.

The acetabulum is formed from the embryonic process of fusion of the ilium (top of the hip), the ischium (lowest part of the hip) and the pubis (below the ilium but above the pubis) and the acetabular bone. Most researchers feel that normal development requires close conformity (close, tight fit) between the acetabulum and the femoral head throughout their growth period. In other words, the joint must fit tightly, deeply and snugly. This is how a puppy's hip starts out-dysplastic and non-dysplastic puppies' hips are indistinguishable. The first six months of life seem to be the most critical growth period when the depth of the socket must be maintained. It is believed that the depth of the socket in the growing puppy may be in part a function of the amount of stress the femoral head can produce on the immature acetabulum. Think of it as a thumb pushing into a ball of clay. The harder the thumb pushes, the deeper the indentation in the clay. Much as a knife edge concentrates force onto a relatively small surafce area (and a pin of a diameter equal to the width of the knife edge even more), the two phenotypic traits that maximize the forces between these two developing bony structures are a small femoral head and a long femoral neck. Note, however, that the normal acetabulum is well-formed in utero, thus the stress may only serve to maintain that socket depth.

To cushion the force between these two bony surfaces, there is a truly remarkable substance called articular cartilage. This cartilage is similar to a hard sponge with a slick hard surface facing the interior of the joint. In the normal joint, articular cartilage is able to change its shape slightly when force is applied to it, thus spreading and distributing force more evenly into the subchrondal bone directly beneath the articular cartilage. This is of major importance to the long-term integrity of the joint.

Holding everything in place is another structure that does more than just enhance the stability of the joint. The joint capsule is a fibrous structure filled with synovial fluid that surrounds, isolates and protects the joint. This joint capsule is essential to proper development and functioning of the joint. This structure is similar to the rubber grease bladder around a ball joint in the front suspension of your car. The cushioning effect of the grease with the fluid pressure of the grease and the elasticity of the bladder helps to stabilize the joint. The bladder helps keep out contaminants. This function becomes even more important as the joint ages and surfaces become worn. The joint capsule contains the all-important synovial fluid, the most important ingredients of which are nutrients, which diffuse into the joint from the blood supply, and hyaluronic acid (HA). The tissues within the joint extract nutrients from the synovial fluid in which they are bathed.

Hyaluronic acid has a critical function: to provide lubrication. This slippery and viscous substance prevents rapid erosion of the articular cartilage and the surfaces of the femoral head and the acetabulum. A membrane called the synovial membrane lines the inside of the joint capsule, providing further isolation of the joint space. Should the synovial membrane become injured or ruptured, white blood cells release enzymes and oxygen radials (free radicals) that attack and destroy hyaluronic acid. When this occurs, the loss of HA reduces the lubrication that prevents friction and limits erosion of the articular cartilage. Even worse, loss of HA allows the enzymes from white blood cells to join forces with oxygen free radicals and attack the articular cartilage. Free radicals play a major role in degenerative arthritis.

The ball-and-socket (coxofemoral) joints of an affected puppy radiographically appear to be structurally and functionally normal at birth. The hips of an affected puppy are indistinguishable from a normal puppy at birth. This is an important point to remember. As an affected puppy grows, the hip joint undergoes severe structural alterations. The changes result from joint laxity and adulteration/destruction of the constituents of the synovial fluid and subsequent loss of lubrication and nourishment, which serve to reduce the regenerative and elastic (force-absorbing and distributing) properties of the articular cartilage. The normal joint retains its tightness and close fit. Whereas in the genetically dysplastic-to-be puppy, the acetabular rim and femoral head become eroded.

Remember that the acetabular depth is partially a function of the small "footprint" of the femoral head which concentrates force into a small surface area. As the femoral head is flattened, the coxofemoral joint no longer fits snugly. Excessive force is applied unevenly, especially at the edges of the flattened femoral head. Visualize this joint looseness as the difference between the impact of a boxer's fist when the punch is thrown with the glove already in contact with the opponent's jaw as contrasted with an initial stand-off distance of say 20 inches. In the first case, little impact force is transmitted and no damage is done; in the second, there may be a knock-out. In the joint, the increase in stress results not only in abnormal wear of the articular cartilage, but causes tiny micro-stress fractures to appear in the subchondral bone. The body attempts to heal these fissures, causing the acetabulum to become filled in, i.e., made shallower. It is this cycle of damage and repair (osteophyte formation) that leads to deformation of the joint, and degenerative hip disease.

Conclusions: Hip dysplasia is not something a dog acquires; a dog either is genetically dysplastic or it is not. Initially, the hips of affected and normal puppies are indistinguishable. Later in life, an affected animal can exhibit a wide range of phenotypes, all the way from normal to severely dysplastic and functionally crippled. You should take away from this article the idea that hip dysplasia is genetically inherited. Never believe a fellow breeder or fancier who claims there is no hip dysplasia in his or her line. Never believe breeders who claim that if their breeding lines carried the genes for hip dysplasia they would be able to see it in their animals' gaits. This just is not true.

Although work has been started to find the genetic markers for the disease, we have as yet no method of genetic analysis that can tell breeders whether their dogs are dysplastic or not. We only have physical expression of the disease, and an effort to "back door" into clear stock for breeding purposes. Breeders must come to understand that the only way to reduce the incidence of hip dysplasia is by trying to breed from as few animals that have progenitors, siblings, get, or get of siblings that had clinical manifestations of hip dysplasia. Obviously, a great amount of information is lacking to make a rational breeding choice. These are hard words to have read, but much of our problem has come from thousands of years of less than natural selection resulting from the domestication of the dog.

In our second article in this series we will address in greater detail the parts nutritional, environmental and other factors play in mitigating or increasing the physical expression of canine hip dysplasia.

Credits

References

^[1] Olsewski J.M., Lust G., Rendano B.T., et al. "Degenerative joint disease: Multiple joint involvement in young and mature dogs." Am J Vet Res. 1983; vol 44:1300-1308.
^[2] Smith G.K., Biery D.N. "New concepts of coxofemoral joint stability and the development of a clinical stress-radiographic method for quantitating hip joint laxity in the dog." J Am Vet Med Assoc. 1990;196:59-70.
^[3] Ibid., p. 59.
^[4] Cargill J. "Truth in advertising: breeder self-regulation I." Dog World. 1990(Jul);75 No.7:38-82.
^[5] Cargill J. "Truth in advertising: breeder self-regulation II." Dog World. 1990(Aug);75 No.8:111-116.
^[6] Cargill J. "What should 'champion' mean?" Dog World. 1993(Feb);78 No.2:34-35.

Links

Dog Genome Project, A scientific study of the chromosomes in dogs. Also information about genetic disorders in dogs.

Next, go to Part II

Genetics And Breeding Strategies: Essays For The Dog Breeder

By Dr. Susan Thorpe-Vargas
Reprinted with permission.

Portions of this book appeared as articles co-written with John C. Cargill, M.A., M.B.A., M.S. and D. Caroline Coile, Ph.D. Used with permission.

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system known to exist now or in the future without permission in writing from the publisher.

Limits of Liability and Disclaimer of Warranty:
The authors and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising out of, the furnishing, performance, or use of the information and suggestions contained in this book.

Cataloging-in-Publication Data is available upon request from the Library of Congress

ISBN 1-929242-17-4

• Introduction: Dog breeding moves to the next level
• Chapter 1: Extraordinary diversity
• Chapter 2: A genetics primer
• Chapter 3: What you get is not necessarily what you see!
• Chapter 4: Ethics and breeding strategies
• Chapter 5: The shallow end of the gene pool
• Chapter 6: Cancer, immune problems and vaccinations
• Chapter 7: And what of the future...?
• Appendix 1: Mapping out the dog's genetic future
• Appendix 2: Glossary
• Appendix 3

Introduction
Dog breeding moves to the next level

Why the dog opted to share his fate with man may never be known. I suspect it had something to do with filling his stomach, but when he did so, mankind took on a moral and ethical obligation. When individuals started to selectively breed dogs for their own ends, their responsibility increased. How have dogs done under our stewardship? It seems that in many cases we have "improved" Canis familaris into a genetic nightmare. Today we have purebreds with a multiplicity of health problems that affect the quality and longevity of their lives while simultaneously sending the cost of dog ownership skyward!

Many people believe that an excess concern for cosmetic attributes has produced beautiful dogs that may get lost at the end of the leash. Today we have many breeds of "designer" dogs have been created through selective breeding that cannot whelp freely or breathe correctly. Every year billions of veterinary dollars are spent ameliorating the effects of this tampering. Is it too late? For some breeds it may be. If they were a wild species, certain breeds of dogs would be on the endangered list. That is why I have written these essays. If you are a breeder, I want to make you aware of the latest information on genetics, what you can do to avoid health problems, and screening technology. If you are a purebred dog enthusiast, this information will help you understand the awesome challenges breeders face.

I believe that anyone who loves his or her breed needs to know more than rudimentary genetics. The modern dog breeder should keep abreast of the very latest information available and take advantage of recent technological advances. What if you could screen your dog for all sorts of genetic diseases, or double up on the probabilities of a trait's expression of a behavioral trait such as the herding instinct or scenting? Even though the technology has not yet reached this stage, it is coming. With the human, canine, porcine, mouse and other genome projects under way, the breeding game has now progressed to the next level. Only breeders - each, acting individually - can address these problems.

Some of this material may be heavy going, but persevere. If your eyes start to glaze over, put the book down for a bit... and then pick it up again. The basics of genetics will be covered as well as such diverse subjects as the origin and domestication of the dog, a mini primer on Population Genetics, the techniques being used to discover the causes of genetic disease at the molecular level, and the tests currently available to breeders for genetic screening. I hope you will find this journey exciting and maybe it will encourage you to explore further.

Some of you question the need for such a book and ask yourself why it should concern you. Robert Jay Russell Ph.D., zoologist and breeder of Cotons de Tulear, put it succinctly¹:

"Every breeder has the ability in a free society to "determine his or her own stopping point." But, a single breeder's actions may have consequences that are far-reaching. A breed is necessarily maintained by a society of breeders. As such, the actions of each breeder affects the actions of every breeder who dips their brush in the gene pool and every buyer - present and future - who buys one of these 'works of art.' Pragmatically (and ethically), a breeder loses his/her right to independence and his/her ability to be independent the minute he/she puts up a shingle that says 'Puppies for Sale.' "

About myself: I thought the best way to start was to talk about my own personal experience with breeding and my relationship with other breeders and "puppy people." All of us "in dogs" started somewhere, and not all of us had the good fortune to grow up in families that were well dogged and involved in breeding, show or other dog activities. My first Samoyed (my first ever dog) was a rescue but my family immediately fell in love with the breed and wanted their very own puppy. We had never had a puppy before and were not dog people. The people we got from rescue had a Christmas litter so we bought a bitch puppy from them as a present for my son. These people were one step up from backyard breeders as they did do some showing and they did do "rescue," but they had litters to make money. This Christmas puppy, call name Shisu, turned out to be my "foundation bitch" and I was extremely lucky with my choice, only I didn't realize it at the time. Shisu came into heat three times between six months and a year old. My vet told me either to breed her or fix her as this "girl wanted to be a mother." So, I called Shisu's breeder who said, "I have the perfect choice for a stud, you should breed her to her grandfather." So we did. The litter decided to arrive on Thanksgiving Day and the first puppy was breech. With my vet on the phone, I was walked through the process and was able to help Shisu deliver nine puppies, one of who later died. (We think the mother stepped on her) At six weeks, I put an ad in the paper and sold the puppies to whoever had the money. To this day, I have no idea what happened to those puppies.

What's wrong with this picture?

• The people who sold Shisu to me should have never sold a puppy at Christmas time. Leaving her mother and littermates was probably that puppy's or any puppy's most traumatic experience of her/their life. All the turmoil and confusion associated with the holidays is not an environment conducive to introducing a puppy to a new household, especially a family that had never had a puppy before.
• I had no experience with young dogs, and did not know what questions to ask. Knew nothing about the breed-hadn't done my "homework" and the breeder had done no genetic testing of her dogs.
• I bred a dog that was too young and had had no genetic testing done. Did not know what were the genetic diseases common in her breed and what, if any testing was available.
• I did not carefully plan the litter, studied no pedigrees, used a sire that was to closely related, and had not undergone any genetic clearance.
• I was neither physically nor mentally prepared to help whelp the litter, nor did I have the proper equipment, i.e., a whelping box with pig rails. I should have had an experienced breeder with me or at the very least, assisted at a few whelpings. I put both my mother dog and her puppies at risk because of my inexperience. Fortunately, Shisu turned out to be a very good mother, but what if she hadn't?
• I did not have a list of qualified puppy buyers prior to the breeding of her bitch.
• I placed her puppies through an advertisement in the paper. Did not require even the most basic criteria of my puppy buyers. I did not offer any guarantees nor did I have a puppy contract. One point in my favor: I did not sell her puppies to a pet store.
• I let those puppies go out in the world with no help offered to the new owners nor anyway to keep track of them.

I did not breed again for four years. I did a much better job the next time.

I learned that if you are a dog breeder, the purpose of having a litter is to provide yourself with a dog that you feel will better the breed, or at least maintain a high status quo with the best. However, every puppy you produce is not a show/performance quality dog. If you do not recognize this, then you are seriously deluding yourself. A side effect of producing your next show or performance dog is that you will always have pet quality dogs to place. Your responsibility to them is just as significant as it is for the dog/s you are keeping for yourself--maybe even more so. One should breed only dogs that have good temperament and good health. Again I have an example of what not to do:

I bought a bitch puppy from a very well known kennel that matched the phenotype of what I wanted to breed. This girl came from a litter of six, but only two survived. (Warning bells should have been ringing here.) After this girl reached two years of age and had passed her hips and eyes exams she was bred to a dog that was related to her seven generations back. She produced eight healthy puppies, all of which survived. She, however, developed eclampsia. Eclampsia is a life threatening condition involving an imbalance in the blood calcium levels. She was pulled through this situation but shortly after weaning her pups she started to get seriously dog aggressive. This behavior only worsened when I started to show her again and she became useless on the sled team. When I complained to the breeder, I was told to return her, and we did. Within a year of returning her, this dog had finished her championship and had been bred to her father. Her breeder obviously had no moral dilemma but I believe what she did was unethical. This girl should never have been bred again. Her life was put in jeopardy by whelping for a second time and such close inbreeding practically guarantees an increased probability that she would pass her poor temperament on to her offspring.

Regardless of the moral stances taken, it seems to us, there is a very real responsibility to breed carefully to avoid creating a cadre of genetically sick dogs. Registries will be forced by population genetics realities to modify their views of what constitutes purebred dogs. Breeders need to rethink their understanding of the benefits of line breeding and other such tight inbreeding schemes in favor of assortive matings to preserve genetic diversity. Those involved in breeds with few founders will run up against genetic reality sooner than some others. There is near certainty that there will be a day of reckoning where the genetic choices made in the past will determine the dogs of the future.

NOTE: Words that are in bold type when they first appear are in the Glossary.

Chapter 1
Extraordinary diversity

Have you ever wondered at the extraordinary diversity in the appearance of various dog breeds? How is it that a Yorkshire Terrier can be the same species as a Bullmastiff, or a Pug be related to a Saluki? What are the factors that have led to this incredible range and variety in appearance, not to mention behavior and temperament? It is not simply a question of phenotype vs. genotype, or dominant vs. recessive genes. Let's begin the journey by looking at how dogs evolved into the companion we know and love today.

Why so many dog breeds?

About 60 million years ago a small weasel-like animal lived in many parts of Asia. This ancestor of all modern day canids (dogs, jackals, wolves and foxes) was called Miacis. Cynodictis, the first true dog-like canids are thought to have descended from Miacis about 30 million years ago. This line eventually split into two branches, one in Africa and the other in Eurasia. The Eurasian branch was called Tomarctus and was, until recently, thought to be the progenitor of wolves, dogs, and foxes. However, new research has called this theory into question with a recent paper indicating now that the wolf is the domestic dog's only direct ancestor and that a recently shared ancestry with the fox and jackal is unlikely.² This somewhat controversial paper also asserts that the first domestication of wolves may have taken place as long as 100,000 years ago. The actual time that such domestication occurred, of course, cannot be settled based solely on DNA analysis.

Research now suggests that the domestic dog line began to diverge from the wolf after the first wolf became domesticated. Over time, groups of wolves became adapted to a niche that made them ultimately better suited to domestication at some point as early as 100,000 years ago to as late as 14,000 years ago. The actual timing remains in dispute since the fossil records are not consistent enough to pinpoint an exact period of time. However it has been well established now that different domestication events did occur from multiple populations by researchers such as Robert Wayne³. This makes sense as both wolves and humans coexisted over a wide geographical area and it is likely that multiple domestication opportunities would have arisen. These multiple events in various parts of the world accentuated the diversity we see in dogs today.

As hunter/gatherers, humans would have found dogs very useful. Then, about 8,000 years ago, humans turned to a more settled way of life. This is when severe selection for specific behaviors and traits became important and 'modern' breeding practices started. And so it begins - dogs bred for many reasons, from companionship to guarding abilities and so on.

The concept of a "pure" breed is a relatively recent one; further back, local dog populations consisted of similar looking dogs bred for a specific purpose. Although there were some exceptions, the dog breeders of that time did not hesitate to breed a dog of one type to a newly arrived dog from another area. Thus, up until the 19th century the various dog breeds were more often than not strains of closely related and similar looking dogs that as a population had a great deal of genetic diversity. Only dog populations that lived in geographic isolation approach today's purebreds in terms of a restricted gene pool.

In searching for cultures without dogs since pre-historic times we come up empty handed. Thus we find early recognizable breeds coming from the Middle East, Africa and Asia. The Middle Eastern coursing hounds had become well established no later than 2,000 BC. The Basenji, a hunting breed of the African savannah, may predate the dogs of the Pharaohs. In the Far East, isolated areas such as Tibet and Mongolia produced a number of still extant breeds of ancient origin. Malta was occupied as early as 3,500 B.C and the dog brought to Malta may have had earlier Egyptian origins. The point here is that since relatively early times in recorded history, there has been a tremendous diversity in dogs. Contrast the Roman Mollosus - a mastiff-like creature (or what we think it looked like)--with the Maltese or the Tibetan terrier or the Lhaso Apso, and it immediately becomes obvious that there may be no "standard" dog. The tiny kingdom of Tibet, produced many different breeds, some now probably extinct, but which include the following breeds and their ancestors: Kuvasz (before Hungary); Lhaso Apso, Tibetan Terrier, Tibetan Spaniel, Tibetan Mastiff, just to mention a few familiar to Western dog fanciers. Even dogs we think of as "English" such as Mastiffs have had ancient origins. Recognizably mastiff-like dogs can be seen on Egyptian monuments circa 3,000 BC. They were in China circa 1100 BC and eventually went to England with invading Roman forces in the first century AD. We can safely say that certain dog strains have been breeding true for a very long time.

Neoteny - More fuel for diversity

There is a saying among dog breeders that "All puppies look alike." Newborn puppies of different breeds, except for size and of course color, look remarkably alike. How is it that they grow up to look so different from one another? The vast array of physical and behavioral differences in dogs is probably not due to selection for each individual trait, but more likely to selection for groups of traits that are all similarly affected by the same hereditary mechanisms. One such mechanism is the regulation and timing of developmental processes. Selection for one trait affected by developmental timing could inadvertently select for other traits also thus affected.

It is very likely that this process has played a vital role in the initial domestication and later diversification of dogs. As animals mature, they pass through different stages, each uniquely adapted to its particular circumstance. In wolves, neonates and juveniles are dependent upon parents to care for them, and they are extremely successful at eliciting that care. In comparison to adults, they are relatively tame and subservient. Wolves (or the wild ancestors of wolves and dogs) that tended to retain these immature qualities of tameness and subservience into adulthood would have been favored by early humans and would have formed the core of primitive domesticated dogs. This retention of immature characteristics in adults is known as neoteny. By choosing the individuals to reproduce that showed the favored immature behavioral qualities, concurrent selection for other juvenile traits -both wanted and unwanted--may very likely have occurred, laying the basis for the diversity seen in dogs today.

Now, let's take a look at some of the basic concepts of Genetics that every breeder needs to know. Then we'll discuss the mechanics of inheritance in Chapters 2 and 3.

Chapter 2
A genetics primer

Are you mystified by the genetic code? Do you blanch at words such as allele, dominant, and codon? Do you think of microsatellites as small orbs circling the Earth? The time is coming when such words will be part of the everyday vernacular of dog breeders. The study of genetics has previously been the domain of specialists, but it is rapidly becoming part of the responsible breeder's repertoire. The study of genetics is much like learning a foreign language. It really isn't all that difficult to become conversational once you master the rules and become comfortable with a new vocabulary.

Genetics 101 - Basic concepts

Each cell within the body is composed of cytoplasm, a jelly-like layer of material that surrounds a nucleus. Within the nucleus are a number of threadlike chromosomes that are almost entirely made up of two kinds of chemical substances: nucleic acids and proteins. Nucleic acids have at least two functions: to pass on hereditary characteristics and to trigger the manufacturing of specific proteins. The two classes of nucleic acids are the deoxyribonucleic acids (DNA) and the ribonucleic acids (RNA). DNA, the genetic building block, is made up of substances called nucleotides, each of which consists of a phosphate, a sugar known as deoxyribose and any one of four nitrogen-containing bases. These four nitrogenous bases are adenine (A), thymine (T), cytosine (C) and guanine (G). Canine DNA is about 6 billion nucleotide pairs long. Each base is attached to a sugar molecule that is linked by a hydrogen bond to a complementary base on the opposite strand. These bases are complementary because only adenine pairs up with thymine, and only cytosine pairs up with guanine; thus the pairs are AT and CG.

 

Before a cell can express a particular gene, it must first transcribe that specific part of the DNA into messenger ribonucleic acid (mRNA). This is similar to the formation of a complementary strand of DNA during cellular division, except that RNA contains uracil (U) instead of thymine as one of its four nucleotide bases. In the process of transcribing DNA into mRNA, all the T bases are converted to U bases. These bases C, G, A, and U are the alphabet of the genetic code. A sequence of AGT in the coding strand of the DNA thus produces a sequence UCA in the mRNA.

Think of codons as three-letter "words" identifying the bases DNA uses to specify particular amino acids as building blocks of proteins. Normally, codons signal the initiation of a protein chain, its end or a particular amino acid. For example, CUU stands for the amino acid leucine. CUA, CUG, and CUC also "code" for leucine, so there is some redundancy in the system. Notice in this example that it is only the last base that is different (U vs. A vs. G vs. C). The term degeneracy is used when a change in a base does not affect the amino acid being added to the polypeptide.

Breaking down the gene

What is a gene? A gene is the basic unit of inheritance. Genes contain a set of directions for producing a bit of RNA, a protein or a polypeptide. If all goes well, a complete set of genes - one half from each parent - is inherited. If the two copies of each gene are exactly alike, the progeny are homozygous at that locus. When homozygous, only one form of the gene will be passed on. If the gene inherited from one parent is different from the gene inherited from the other, the progeny are heterozygous. In this case, there is an equal chance that one or the other form of the gene will be passed on. Different forms of the same gene are called alleles.

In the dog, the various genes are located among 78 different chromosomes. What is not known is how many genes exist, although a rough estimate has been made that there may be as many as 100,000 or as few as 30,000. It is also not known where on the various chromosomes specific genes are located. In fact, scientists have just recently karyotyped the canine. This provides the ability to differentiate between specific chromosomes. This will be valuable information when scientists are finally able to map the canine chromosome. Such a genetic map will not only allow the determination of the position of genes relative to each other, but also will reveal their approximate distance from each other.

The cell cycle

Mitosis is the process of one cell splitting and becoming two cells. This act of division is the result of a series of events known as the "cell cycle," which consists of several distinct phases or stages. The resting or quiescent state between cellular divisions is called the "G0" stage. "G1" is the phase in which all the cellular proteins needed for mitosis are made and is the first control point where the cell must "decide" to move on to the next stage--the "S" phase. During the "S" phase, the cell's genetic material is duplicated so each of the daughter cells is genetically identical to the parent cells--unless something goes wrong. The S phase is so named because this is the point during which new DNA is synthesized. The period from the end of the S phase until the actual division of the cell is known as the "G2" stage and is the second control point during which a decision is made whether or not to actually undergo division. Mitosis is further divided into prophase, metaphase, anaphase, and telophase. The stages G1, S and G2 constitute the interphase.

In a process called meiosis, germline cells--sperm and eggs- go through one more division in which their DNA is not duplicated. This leaves them with only half the normal number of chromosomes that somatic cells have. Somatic cells are all the cells of the body except the germline cells. Once these two cells combine to form a fertilized egg or zygote, they then have the proper amount of DNA--half from their mother and half from their father. This is important because mutations in the germline cells are passed on to the offspring, whereas those that occur in somatic cells only affect the individual.

Gene mutations

Mutations (changes in the genes) are caused by a variety of mechanisms. Some of the most common are mistakes made when the organism's DNA is replicated prior to a cell dividing. Although there are body system safeguards in place to prevent this from happening, nothing is foolproof, and eventually over time, failure to replicate DNA accurately will occur.

Likewise, errors can occur all along the pathway that leads to the translation of messenger RNA into a specific protein. These errors can occur spontaneously or be the result of exposure to natural and/or man-made mutagens. Certain chemicals or exposure to certain types of radiation can cause genetic changes. What is important to remember is that these mutations are random events with respect to their adaptive potential. In other words, they will happen independently of whether they have beneficial or harmful consequences. More often than not these mutations are harmful, as they are changes to the make up of a living organism. Just how harmful depends upon the type of mutation that occurs and the environment in which they occur. Most mutations fail to thrive, reproduce or survive and thus are not passed on to successive generations. There are several kinds of gene mutations, each having a unique range of potential effects. This is important to recognize because many genetically transmitted diseases result from a specific kind of mutation. Each of these forms of mutation is the result of the organism failing to reproduce its DNA accurately all of the time and subsequently passing these genetic changes to successive generations.

Base-Pair Substitution Mutations

The result of this type of mutation can range from no effect at all to one that has severe consequences to the affected organism. Remember DNA is made up of four different nucleic acids: thymine (T), adenine (A), guanine (G) and cytosine (C), and remember that thymine always pairs up with adenine and guanine always pairs up with cytosine. Hence the name base-pair mutation. Sometimes when the DNA strand is being replicated the wrong base is inserted. This can result in a different amino acid being added to the protein being made. If the essential biological function of that protein is not changed then there is no detectable effect. However, if the substitution affects the active site of an important enzyme or changes it's three-dimensional shape, then it modifies the fundamental nature of the protein. If this occurs along an essential metabolic pathway, the results can be disastrous.

The most unfortunate result of a base-pair substitution is when this mutation codes for a stop codon. Keep in mind that a codon is that portion of the messenger RNA that codes for a specific amino acid. A start codon serves rather like a capital letter indicating the start of a sentence. A stop codon is one that does not specify an amino acid, and serves much as a comma or a period punctuating the genetic message. If, by chance, a mutation produces one of the stop codons, than the process of making the protein is terminated. An example of this type of mutation is the one that leads to a form of progressive retinal atrophy (PRA) in the Irish Setter. A substitution of an A for a G produces the stop codon (TAG) that replaces the normal codon for the amino acid tryptophan (TGG). This prevents a protein called PDEB (phosphodiesterase beta) from being produced in its full-length form. The shortened protein is unstable and is degraded within the retinal cells in which it is needed. The lack of this protein causes the retina to degenerate, resulting in blindness in those Irish Setters that have two copies of the mutant gene, and no normal copy.

Frameshift Mutations

In the normal cell replication process, DNA is transcribed into messenger RNA, which in turn is translated into a series of amino acids. This always occurs in a specific manner, i.e., it always begins at a definite spot and it is 'read' in multiples of three and in a particular orientation along the length of the strand of DNA. This is called a reading frame. If there is an addition or deletion of one or two base pairs, then the result is often a very altered sequence of amino acids in the final protein product resulting in what is termed a frameshift mutation.

An example of this is the mutation that leads to an inherited form of anemia in Basenjis. A deletion of a single nucleotide in the 433rd codon of the gene encoding a protein called PK (pyruvate kinase) causes a shift in the reading frame. The misformed and shortened protein (a new stop codon is ultimately encountered) is unstable in the red blood cells that carry oxygen throughout the body. The lack of the PK causes the red blood cells to slowly be destroyed and results in the anemia.

Splice-Site Mutations

Molecular geneticists used to think that all of the DNA coding for a particular protein was continuous until they started to look at more complex organisms. What they found, in these types of cells, is that the DNA that makes up a gene is often distributed in discontinuous sections called exons, interspersed with long segments of non-coding DNA known as introns. These sections are transcribed into messenger RNA along with the exons, but before the RNA is translated into a protein they are 'edited' or 'spliced' out. A change of even a single nucleotide in one of the exons of the gene can cause a shift or alteration of the splice-site.

A genetic disease that affects Dobermans is a perfect illustration of this type of mutation. von Willebrand disease is a bleeding disorder that effects the animal's ability to form blood clots. Other breeds also have this disease, but what had perplexed those doing von Willebrand research was that Dobermans appeared to have a milder form of the disease. The discovery of a splice-site mutation that codes for von Willebrand factor has cleared up their mystery. George Brewer MD of the University of Michigan suggests that one use the following analogy in order to explain how the mutation functions⁵. Imagine that a freight train is supposed to go from point A to point B along a railroad track. Somewhere between A and B is a spot where a sidetrack goes to point C. Normally, the train never goes to point C because the switch, that connects the two tracks, is never thrown. If the switch is broken (the mutation) then the lock that prevents the track from connecting to point C is no longer effective. The switch can now toggle back and forth, sending some trains to point B and some trains to point C. In affected Dobermans, the defective switch sends the train to the wrong destination about 90-95% of the time, the train rumbles over the cliff and is never heard from again (i.e., the proper protein is never made). However, sometimes the switch jiggles the right way and the train ends up at the normal destination and the proper protein is made. If both copies of the gene are mutated, then each gene can make the right protein about 5 to 10% of the time. Affected Dobermans are thus producing von Willebrand factor at least some of the time and so their symptoms are not as severe. A mystery explained.

Chromosomal abnormalities

Other types of mutation occur during cellular division because of chromosomal abnormalities. Let's review how chromosomes are normally duplicated during cellular division. Keep in mind that the prophase is the first stage of cell division. The nucleus swells and the chromosome becomes visible. During interphase the DNA has been duplicated and consists of two linked (sister) chromatids held together at a centromere. A structure called a centriole appears and moves towards the opposite poles of the nucleus. The next stage is called the metaphase. During this period the spindle fibers are formed and are attached at the centromeres and the chromosomes line up along the equator. This is the very best time to examine the complete set of chromosomes within a cell. If a cell is "fixed" at this point in the cycle and stained with special dyes, a cytogeneticist can determine if there is the correct amount of DNA, any deletions or other abnormalities and the sex of the individual. This "picture in time" is called a karyotype.

Following the metaphase is the anaphase. During this stage, the sister chromatids separate and migrate to opposite ends of the cell, the nuclear membrane has disappeared and the cell elongates as the diameter of the cell decreases at the equator. At telophase a new membrane is formed about the two new cells, the chromatids (now called chromosomes) uncoil and the nucleus is reformed. In sum, chromatids are just compacted chromosomes.

Before looking at the different types of chromosomal abnormalities let us first discuss some of the terms used to describe them. Chromosomes are either sex chromosomes, in mammals these are the well-known X or Y chromosome, or autosomes. Autosomes are any chromosome that is not a sex chromosome. Chromosomes can be divided further into metacentric, submetacentric and acrocentric. These terms describe the position of the centromere within the chromosome. Metacentric chromosomes have their centromere near the center of the chromosome. Those chromosomes whose centromeres are slightly off-center are referred to as submetacentric, while acrocentric chromosomes have their centromere located close to one end. Dog chromosomes are mostly acrocentric. The small "arm" of the chromosome is referred to as p for "petit" and the longer arm is called q - the next letter in the alphabet. Another naming protocol is to designate regions and bands from the centromere outward. Depending on which staining techniques are used, banding patterns are seen that are characteristic for each chromosome pair. Thus, the designation 7q31.2 refers to the long arm of chromosome 7, region 3, band 1, sub-band 2.

Numerical chromosomal abnormalities

Normally dogs have 39 chromosomes in their germline cells, i.e., sperm and eggs. Germline chromosomes are haploid, i.e. they contain one copy of each chromosome. Somatic cells are diploid - they contain two homologous copies of each chromosome. A failure of the chromosome to separate properly during cell division (nondisjunction) can lead to a decrease or increase in the number of normal chromosomes. For example: Triploidy is the presence of three haploid sets of chromosomes, instead of two. Monosomy is the situation where a diploid cell, in which normally one or more of the homologous chromosome pairs is represented, only has one chromosome of the pair. Trisomy is the term used which indicates the presence of an extra whole chromosome. Each canine somatic cell usually has 78 chromosomes (2x39), but in trisomy, this is increased to 79. Down's syndrome in humans is caused by this anomaly as there is an extra chromosome number 21.

Structural anomalies

A chromosomal deletion occurs when part of a chromosome is missing. The damage that can occur depends upon how big of a piece is missing and where the deletion occurs. A chromosomal duplication happens when a section of the chromosome is reproduced twice. Depending on what section is duplicated there can be extra sets of genes present that can cause birth defects or developmental problems. A chromosomal ring occurs when the q and the p ends stick together. This can cause loss of information and/or cause problems when the cell divides. A chromosomal inversion is caused when there are two breaks in one chromosome and the area between the breaks are turned around and reattached. If the break includes the centromere, it is called a pericentric inversion. If not, it is a paracentric inversion.

Chromosomal translocations are rearrangement of a chromosome in which a segment is moved from one location to another, either within the same chromosome or to another chromosome can be balanced or unbalanced. A balanced translocation occurs when the same piece of chromosome, say the q arms of two different chromosomes, are broken off and attached to the other chromosome. No genetic material is lost, it is just on a different chromosome. This should not cause problems with the individual but could with that individual's progeny. An unbalanced translocation, occurring in a germline cell, results in 3 copies of a section of chromosome in one cell and only one copy in the other. Both trisomy and translocation are implicated in canine cancers. The other chromosomal anomalies are well characterized in human disease but not in the canine.

Chapter 3
What you get is not necessarily what you see!

The age-old problem for dog breeders of course is that the characteristics they are trying to breed for do not always materialize in a litter of puppies. Or some unwanted characteristic keeps appearing that even "careful" breeding cannot eliminate. Why does this happen and what can be done to eliminate at least some of the uncertainty a breeder faces?

Gene expression

Keep in mind that the number of genes in the entire dog genome has been estimated to range from 30,000 to 100,000. Thus the breeder is dealing with a very large number of variables. Remember that every gene is the blueprint for either regulatory RNA, a protein or a snippet of amino acid called a polypeptide, but these gene products are not being made all the time nor at the same time. Regulation of expression involves turning genes on and off at various intervals and in a particular temporal sequence.

The first step in gene expression begins with transcription. This is the process of copying a DNA sequence called the template, into a single strand of RNA known as the primary transcript. This operation is initiated by an enzyme called RNA polymerase. Genes come in two types, structural and regulatory. RNA polymerase is a protein that is coded for by a regulatory gene. Transcription starts when this enzyme binds to a special region at the start of the gene called the promoter and continues until it reaches a terminator sequence. The first point of control in this process is therefore the binding of the enzyme to this specific site.

While all genes are present within a cell, only certain genes within any cell express themselves through a process called cell differentiation. Have you ever asked yourself why are the cells in your fingernails only producing fingernail proteins and not, lets say, eye proteins? The simple answer is that all the other genes in the cell, except those coding for fingernail proteins are somehow turned off.

In the process of maturation, a cell progressively and irreversibly becomes more committed to a certain line of development. One of the ways scientists think a cell can 'remember' what it has decided to be seems to depend on the chromosomes. Control of gene expression is the result of regulating transcription initiation. Chromosomes play a unique role in this process. It is possible to see cellular DNA only during certain phases. Most of the time it exists in a relatively uncondensed form and it is only during this dispersed phase that transcription can occur. However, even during this stage, some parts of the chromosomes stay tightly wound up and condensed. The part that is unwound is called euchromatin and it is transcriptionally active. The part that stays condensed cannot be transcribed because the transcriptional factors are physically unable to get to the DNA.

There are two types of inactive chromosomes. One is called constitutive heterochromatin and it is always transcriptionally inert. The other is referred to as facultive heterochromatin and it varies in a tissue-specific manner. So, depending on which cell type it is, large blocks of chromosomes are physically prevented from being transcribed. This constitutes regulation at rather a gross level, a finer aspect of control exists in the specific sequence of the DNA itself.

Another form of gene regulation can result in an entirely new protein being made or, in some cases, no gene product at all. This can happen through the selection of alternative transcription initiation sites or optional splice sites. An additional control mechanism has been suggested by the processing of messenger RNA. It is mRNA that is actually translated into the final gene product. Whether or not messenger RNA makes it out of the nucleus so that it can be made into a protein, or how long it lasts before it is degraded, would definitely affect the final gene product. However, research has barely begun on these topics, so we will leave it for now to discuss another pathway to phenotypic differences.

All alleles are not created equal - dominant and recessive genes

Control of gene expression also depends on how genes interact and their alternative alleles. Because chromosomes are present in pairs, it stands to reason that the genes on them are also present in pairs. Genes in corresponding locations on homologous chromosomes are called homologous genes, and when these homologous genes can code for different proteins, they are called alleles. Sometimes we are aware of only two possible alleles for a particular gene, but often several possible alleles exist. Only two at a time can be present in one individual, however.

The possibility of having either identical or nonidentical allele members of a pair creates an array of different ways these alleles can interact. When one allele can completely mask the presence of the other it is termed complete or simple dominance. If both alleles can be expressed equally then codominance occurs. Sometimes the end result may be intermediate between the products of the two alleles generating incomplete dominance.

The gene can be considered a small business with two partners. Sometimes both partners share the same desires, just as both alleles may code for the same products. This is the situation with homozygous alleles. Sometimes partners, and alleles, don't agree, such as with heterozygous alleles. Heterozygosity can have several outcomes. As in any "partnership", decision making can take several forms. In some cases one partner (the dominant allele) calls all the shots, regardless of the wishes of the other (recessive allele). In genetics this is known as simple dominance. In other partnerships, compromise is the order of the day, and when the two partners are not in agreement, they settle on an intermediate solution (incomplete dominance). In yet other partnerships, both members go ahead and do what they want to do regardless of what the other does. In genetics such a solution is termed co-dominance.

Simple dominance

Dog breeders sometimes fall into the trap of assuming a trait is due to a dominant allele because "even after being hidden for generations it just popped back out... I can't seem to get rid of it". In fact, they have put their finger on the signature of the recessive allele. Consider the case of black versus liver hair color. A single dominant allele (B) codes for black pigmentation. Dogs that are either BB or Bb will be black and indistinguishable from one another. The "science speak" way of describing this is to say that the genotype is different but the phenotype is the same. In the case of two recessive alleles, bb, liver color result. If two liver (bb) dogs were bred together, they could only produce liver offspring. If two black dogs were bred, the possibility exists that both of those dogs could be heterozygous (Bb) and produce a bb offspring that would be liver--not because the liver was dominant, but because it was recessive and thus hidden in the parents. A trait caused by a dominant allele can be traced directly from one ancestor to the next through a pedigree, although, as we will see later, other genes can also act on the dog's color to possibly modify or obscure it. Not all traits are inherited in this manner, however. In fact, most traits do not show simple dominance.

Incomplete dominance

In contrast to simple dominance, in which two alleles produce three possible genotypes but only two possible phenotypes, incompletely dominant allele pairs produce three possible genotypes and phenotypes. The merle coat color pattern (found in breeds such as the Australian Shepherd, Dachshund, and Collie) is an example of an intermediate phenotype created by two non-identical (M and m) alleles. Dogs that are mm have "normal" non-merle coat colors determined by genes at other locations. Dogs that are Mm display the classic merle color, in which areas of the coat have loss of normal pigmentation, resulting in the appearance of flecks or patches of normally colored hair interspersed among lighter hair. Dogs that are MM have greater pigment loss, may be nearly white, and very often have visual and auditory problems that are pigment related. Breeders thus usually discourage merle to merle breeding, since 1/4 of the progeny of a Mm x Mm breeding would be MM - and therefore likely to have vision and hearing problems. Instead, taking advantage of incomplete dominance, merles (Mm) are best obtained by breeding non-merles (mm) to merles (Mm), resulting in litters consisting on average of 50% Mm merles and 50% mm non-merles. Two simple tests can determine if a trait is incompletely dominant. For one, crosses between two different parental types should always result in the intermediate type. For another, crosses between two intermediate types should result in both intermediate as well as parental types.

(3-2 Susan diagram here of incomplete dominance discussion above using letters is ok)

Co-dominance

In yet another example, other alleles code for products that can both be distinguished in the individual. The most common examples of this codominance are usually found in certain blood proteins expressed in both people and dogs. Perhaps the simplest and most familiar are human blood groups. In humans, three possible alleles exist: A, B and O. A and B are dominant over O, but are codominant with each other, thus resulting in the AB blood type.

Penetrance and Expressivity

Just when early researchers thought they had dominant and recessive inheritance clearly defined, they kept coming across cases where an allele that should have been expressed wasn't. The most obvious were in identical twins that weren't quite identical. One would exhibit a trait known to run in that family while the other would not, yet they were identical in all other respects. This is known as variable penetrance. Related to this is the concept of variable expressivity, where both twins would share the same trait, but one would have a more pronounced version of it than the other. Two dogs that both carry the same alleles for spotting may have very different spotting patterns. For some reason some alleles will not always be expressed, or will be expressed to varying extents, in an individual that should normally express them. For the breeder, these two phenomena can make tracking the hereditary pattern of a trait more complicated.

Pleiotropis

Some genes affect widely disparate traits. Chinese Cresteds come in a hairless and powderpuff varieties, with the hairless caused by a single allele H. In fact, this is a homozygous lethal allele, because dogs with HH die before birth so hairless dogs are all Hh. The H allele not only results in hairlessness, but also in tooth abnormalities, which is why allowances are made for hairless Cresteds with missing teeth. Because these two traits are pleiotropic i.e., the effects of one allele, they cannot be separated and one must always go with the other.

In addition to the interactions that occur between alleles at the same locus, interactions can also occur between alleles at different loci. Examples of traits involving different loci include the concepts of phenocopies, linkage, epistasis, and perhaps most important, polygenic effects.

Phenocopies

Sometimes two dogs will seem to share the same trait but in fact the trait is the result of totally different genes. White dogs can result from the alleles for extreme white spotting (basically a spotted dog without any spots showing) or from a dog with several alleles at different loci for factors that make the coat pale (basically a cream dog that is so pale it appears white). The eye disease, Progressive Retinal Atrophy (PRA) exists in many breeds, sometimes appearing clinically identical, even though the genetic cause is different. This means that even though PRA is recessively inherited in affected dogs, crossbreeding different breeds may yield normal offspring because unique genes in the two breeds cause the disease. (If an affected dog of breed A is pp RR, and an affected dog of breed B is PP rr, then their offspring would all be Pp Rr, and appear normal). For example, Irish Setters and Collies have genetically distinct forms of PRA.

Epistasis

Not only can alleles interact with other alleles at the same locus, but in some cases, with alleles at other loci. While dominance can be considered an intralocus interaction, epistasis can be considered an interlocus interaction. The simplest case of epistasis occurs when the presence of one trait effectively masks the presence of another trait. Such an example occurs with Labrador Retriever coat colors. At the B locus, the dominant B allele codes for black fur (BB or Bb) and the recessive b allele for chocolate fur (bb). However, at a totally different locus, E, the presence of the dominant E allows either black or brown fur (according to what is determined at the B locus), but ee restricts the formation of any dark pigment, thus resulting in a yellow dog no matter what is coded for at the B locus.

Another form of inheritance (above the genes) includes a phenomenon called epigenetics. Imprinting is an example of this. Normal development requires genes to be inherited from both parents. Genetic imprinting is the situation where the expression of the gene is determined by which parent you inherited the gene from. Some disease genes are expressed as an entirely different disease, depending upon whether you inherited the gene from your mother or father. Imprinted genes occur in those regions of specific chromosomes with allelic differences in transcription and methylation. A mutation within an imprinting region can cause genetic abnormalities. In humans, Prader-Willi syndrome (PWS) and Angelman Syndrome (AS) are examples of two different disorders, with entirely different phenotypes, that are caused by either a maternal or paternal deletion on chromosome 15 or when the inheritance of both chromosomes is from just one parent (uniparental disomy). Only paternal deletions are seen in PWS and only maternal deletions are seen in AS. When both copies of chromosome 15 are inherited solely from the mother the disease presents as PWS and just the opposite when AS is seen.

Polygenes

The problem dog breeders have with using ideas of dominant and recessive genes in breeding dogs is that most traits don't appear in discreet intervals, but instead are continuously distributed over a range of values. This is also called a quantitative trait. For instance, dogs don't come in just short, medium, and tall, they come in all sizes. Even within a breed, height is normally distributed in a bell curve. This is because many important traits are the result of many pairs of genes acting together. In these cases, the extent of a trait is determined by gene dosage, which is the number of particular alleles present in a genotype.

Imagine that height is controlled by incompletely dominant alleles at three different loci, A, B, and C, with A+, B+, and C+ all coding for an additional half inch of height. A dog with the genotype A+A+, B+B+, C+C+ would be three inches taller than one with the genotype AA, BB, CC. In fact, 27 different genotypic combinations are possible in this example, resulting in seven different heights. The more loci involved, the greater the number of possible genotypes and phenotypes, until the phenotypes become so numerous that they appear to be continuously distributed. This blending is further influenced by environmental factors. In fact, all quantitative traits have an environmental component. A good example of this in the canine would be hip dysplasia. Hip dysplasia is a disease that is known to be influenced by the amount and quality of food that the puppy eats.⁶

Heritability

The fact that gene expression can be influenced by the environment should not be surprising. The value of how much the expression of a trait is genetically determined is called heritability. This value ranges from 0 to 1 and the higher the value the more likely that selection will play a role in the inheritance of that trait. What should also be stressed is that the heritability of a trait in one group cannot be compared to that of another group. Heritability is strictly a function of a particular population, at a specific time and place. One should also be aware that no matter how high the genetic heritability of a trait there will always be some environmental component in the expression of that trait.

Linkage and Linkage Disequalibrium

In a highly inbred population, genetic defects can become fixed rather rapidly if they happen to be on the same chromosome as a gene that codes for a desirable trait. The closer they are physically on the chromosome the tighter they are 'linked'. These genes and their respective alleles will be inherited together unless they become 'unlinked' in a procedure called crossing over or recombination. This is a process that occurs during the formation of gametes. At that time, homologous chromosome pairs exchange segments of their DNA structure. Such closely linked genes are said to be in a state of linkage disequilibrium. When a breeder selects for or against a specific gene trait, he or she may also inadvertently be choosing other traits which are located on the same chromosome. One should remember this when making a breeding decision. Severe selection pressure against an unwanted trait could result in throwing the baby out with the bathwater and the permanent loss of a necessary or desirable attribute.

Sex Linkage

A special case of linkage exists when genes are located on the sex chromosomes. Unlike the other 38 pairs of chromosomes, the sex chromosomes are not always paired in a homologous fashion. This is simply because sex is determined by whether an individual has two X-chromosomes (XX=female) or an X and a Y chromosome (XY=male). The Y chromosome is a very small chromosome and until recently there were doubts that any significant information was contained on it. Those genes found on the Y chromosome that have been identified, code specifically for male traits. The X chromosome is larger and is known to carry on it genes that code for several traits important for males as well as females. Genes on the X chromosome are not matched by genes on the Y chromosome, negating the possibility of allelic pairs.

In the male, whatever alleles are on his single X-chromosome will be expressed (a condition known as hemizygous). In the female, the situation is different than what is seen in the autosomal (nonsex) chromosomes. For many years it was assumed that X-linked alleles acted just the same as autosomal alleles. They don't. Instead of acting in a standard dominant/recessive way, these alleles act more like codominants. In placental mammals one of the two X-chromosomes is randomly inactivated in each cell of the body. The remnants of these inactivated chromosomes can be seen as dark spots, called Barr bodies, in almost every cell of a normal (XX) female, but not in normal (XY) males because they must have a functioning X chromosome. However, researchers at the National Institute for Medical Research, UK, have recently discovered that the "silent" X chromosome in females is not entirely silent - some of the genes evade inactivation, meaning females actually express more genes than their male counterparts. Approximately, 15% of genes escape inactivation altogether, each of which now becomes a candidate for explaining some differences between males and females. In addition, another 10% are sometimes inactivated and sometimes not, giving a mechanism to make women much more genetically variable than men.

Very early in embryonic development both X-chromosomes are apparently active, but then most of the duplicate chromosomes are rendered dysfunctional by staying tightly condensed in the heterochromitin state. It is entirely a matter of chance whether it is the paternal or maternally derived X chromosome that is inactivated in any given cell, but once inactivated; all subsequent cells derived from that cell will continue to have the same inactivated X chromosome. In individuals with visible sex-linked traits the results can be clearly seen as patches of paternally and maternally derived traits. Thus, all female mammals are mosaics.

The best known example is the calico cat, which is almost always a female (the few males are abnormal XXY individuals) displaying a patchwork of black and orange colors, each patch representing a clone of an original cell that randomly inactivated either the X chromosome with an allele for orange fur or a the X chromosome with the allele for black fur. In dogs, we have to look a little more carefully for such evidence. Examples include X-linked muscular dystrophy in Golden Retrievers and X-linked hereditary nephritis. Because these female carriers are mosaics for the abnormalities seen in these diseases, they may exhibit attenuated signs of the disorder, with the severity depending upon the proportion of the mosaic derived from the X chromosome that carried the abnormal allele. Sex-linked traits will be passed from dams to sons via one of her X chromosomes. Because sires have only one X chromosome to pass on to their daughters, in order for the trait to be fully expressed in a female, she must have an affected sire and carrier (or affected) dam. The degree of mosaicism that the dam expresses is random and does not affect the chances of her offspring being affected or the severity of that trait in those that are.

Misunderstandings about sex-linked inheritance have given rise to many breeding myths, the most widespread of which place greater emphasis on the "sire line" (sire to grandsire) in the belief that "what you see is what you get" is due to the single X chromosome, as well as the belief that important breed attributes are carried on the Y chromosome. Some also contend that whether an ancestor is on the dam versus the sire's side of the pedigree is of prime importance. These theories neglect the fact that the Y chromosome contains few, if any, identified genes apart from those involved with male reproduction, and that that the sex chromosomes are but one of 39 pairs of chromosomes. These ideas served the 19th century breeder well enough, having been developed well before the birth of genetic science, but they have no place in the 21st century breeder's arsenal.

So, the variety of appearance between dogs of different breeds is controlled at several different levels. Some types of expression seem to depend upon turning control/regulatory genes on and off so that a specific developmental cascade is expressed. Other phenotypic differences must rely upon the interaction of genes, their various alleles and where these hereditary units are located on the chromosomes. Hopefully, the modern breeder will be able to use this knowledge to make more informed choices when planning a breeding or to understand why certain breeding decisions went awry.

Chapter 4
Ethics and Breeding Strategies

The canine species as a whole maintains a tremendous genetic diversity. Indeed, it is the "plastic" nature of the canine genome that has allowed the creation of such a variety of different dog breeds. By selection for certain behaviors and the physical requirements needed for a particular occupation, humans were able to fashion breeds as morphologically different as the Yorkshire Terrier and the Newfoundland. However, in establishing specific breeds, both breeds and individual dogs have lost genetic diversity. What does this mean to the fancy?

It is a fact that every dog--and human for that matter--carries deleterious genes. It is nothing to be ashamed of it is just a fact. Nevertheless, many breeders feel that they must inbreed or, more euphemistically, linebreed in order to maintain type. However, when you inbreed, you not only double up on the "good" genes, or those that you are selecting for, but you are also doubling up on recessive traits that are at the least suboptimal and which, at the worst, express genetic disease. If the trait is polygenetic, like hip dysplasia, then you are probably adding to the "threshold" genetic load at which that disease is expressed. The choices and priorities of individual breeders have a tremendous impact on the continued viability of their specific dog breeds. The question one should ask oneself is, are you breeding for yourself and your ego or are you seeking the betterment of, and indeed the continued existence of, your breed? Let me suggest that some current breeding practices are neither in the best interest of the individual dog in terms of health and temperament, nor do they bode well for breeds the future.

Breeding questions

So what defines a breed? It has been suggested by Jeffrey Bragg in an internet article entitled "Purebred Dog Breeds into the Twenty-First Century - Achieving Genetic Health for Our Dogs" (www.siriusdog.com/bragg.htm) that three concurrent criteria have to be met before one can declare with certainty that, yes, this is a distinct breed.

Dog breeds are first distinguished by ancestry. This means that all the dogs of a certain breed can trace their pedigree back to a select group known in breeding parlance as founders or foundation stock. The next condition is that they have been created for an express purpose, i.e., they all have a specific job to fulfill. Thirdly, they all must share a particular physical appearance that subsequently has been defined and refined into what is now known as the breed standard.

Originally, that breed standard may have reflected the type of work required of the dog but sadly, this may no longer be true. The Bulldog is a good illustration of how exaggerated type (appearance) has led to the creation of a dog no longer capable of performing its original function, which was bull-baiting--setting Bulldogs on a tethered bull with the purpose of pinning and holding it. The breed has lost its agility and now would get stomped or gored by a bull. The bracycephalic face makes it impossible to take in enough air to support that vigorous activity and leads to overheating.

The case can be made that rigid selection for appearance and preference given to breeding partners, based on a closed and genetically isolated population derived from a particular foundation, has resulted in the loss of genetic diversity and the steadily declining health of the purebred dog. In addition, little or no emphasis is often placed on performance factors for which the dog was originally bred. Even though many do not acknowledge there is a problem, modern breeders are now in a quandary because they have failed to recognize that techniques needed to establish a breed (such as extreme inbreeding) are detrimental to the continued existence of that breed.

Dog breeders are a group with long traditions and many "rules of thumb" that are contrary to known scientific facts. Far too few dog breeders have had any exposure to basic genetics, much less population genetics, to assist them in making informed mating decisions. Population genetics involve a population or species as a whole, rather than concentrating on the individual animal. Population genetics is a very useful tool for showing what happens when we lose genetic diversity. Our worldwide purebred registries were developed on presumptions that predate genetics and that do not hold up to scientific scrutiny today. The idea that inbreeding is not problematic is the prime example. This must change if we are to save the sport of dog breeding and showing.

When discussing the need for changes, many "old line" breeders argue, "Genetics is just a science based on theories, and theories have often been proven wrong by newer theories." One sees comments on various Internet breed lists alluding that no one person's theory has more value than another is because they are only opinions.

Theory and scientific opinion are often misused and misunderstood terms. To a layperson "theory" means speculation, but in truth, anything in science that gets elevated to the status of a theory has an overwhelming amount of evidence that supports it and has, in fact, withstood many challenges. Theories bring together and elucidate a large chunk of information and help us to understand and organize a wide range of topics.

Inbreeding and the purebred dog

So what has science shown us? In order to create a uniform type which breeds true, one must inbreed. Inbreeding is the mating of two animals that are more closely related than the average individual within a certain breeding population. When breeds were formed, usually just a few dogs were used as founders. As a result, many existing breeds are more than 20 percent ancestrally inbred, as shown in Daniel L. Hartl's and Andrew G. Clark's "Principles of Population Genetics."⁷ To illustrate let us look at the Samoyed, a breed that started from a foundation stock of fewer than 20 dogs. British explorers had already taken some of the dogs of the natives local to the Bering Straits for sled dogs in their quest for the North and South Poles. Taking a small population from a major population in this way is called a founder event. The British had rather severe selection criteria: The dogs were to be white, have dark eyes, dark eye rims and solid black lip lines.

Compounding the problem of a limited number of founders was the overuse of several of these foundation animals, and the underutilization of the others. This artificial selection was necessary because inbreeding alone is not sufficient to "fix" characteristics and eliminate unwanted traits. Artificial selection refers to nonassortive mating in which selection pressures are determined by purely aesthetic factors. For example, a human deciding he or she likes red coats. So inbreeding and artificial selection were used to fix type by increasing the homozygosity of the genes that coded for appearance. In addition, many other traits not expressed in the phenotype also became homozygous. This practice also resulted in a loss of genetic diversity and the fixing of gene frequency. This means that the frequency of certain genes found within the source or original population are not necessarily reflected in the new founder population. It all depends on what genes the founder animals brought with them. Thus a genetic defect that was very rare in the source population can become very common in a particular breed because one or more individuals in the new population carried that defect. Compounding the problem is the fact that small populations are subject to genetic drift. Genetic drift is the random loss of alleles due to chance. As explained above, alleles are alternative forms of genes at the same position on a chromosome. Having multiple alleles at a particular locus within a population is a measure of that population's genetic diversity.

One way to illustrate the concept of genetic drift is to think of a coin toss. The probability is 50:50 that either side will come up. However, if you toss the coin only three times, it is not all that unusual for you to get three heads or three tails. It is only by increasing the number of tosses that you start to get the normal probability. This is called the Law of Large Numbers. Think of the number of tosses as the number of individuals in a population--the fewer the number of individuals, then the fewer the number of alternative alleles available. Also adding to the problem is the fact that not every individual is chosen to produce progeny, so his or her genetic contribution is lost forever. The actual number of individuals that produce progeny (as opposed to the total number in a population), may be surprisingly limited in certain breeds. To illustrate, imagine you have a very popular breed with thousands of registrations yearly. What if only 300 males are used to provide stud service? Anything that restricts the number of males used will limit the effective population. This uneven use of individuals in breeding remains a factor today and is called the popular sire syndrome.

Line breeding and inbreeding

Dog breeders have for years expounded on the merits of line breeding as opposed to inbreeding. Some claim that line breeding has no deleterious effects. This is just not so. Line breeding is not a recognized term in genetics - it is all considered inbreeding. The late geneticist, Dr. John Armstrong of the University of Ottawa, Canada so elegantly wrote,⁸

In my view, one could probably subdivide inbreeding into three categories: background, historic and recent. The background level is dependent upon the number of founders. In a breed/population that started from six or eight founders, sometimes closely related, you cannot find individuals that are not related even if you breed as carefully as possible. Recent (or "close") inbreeding is, to me, the breeding of sons to mothers, full siblings, and the like. When it isn't done simply for the convenience of the breeder, the usual justification is that it is the only way to preserve type, or that it is an effective way of discovering problems in your line. Yes, genetic defects can be uncovered in this way, but in practice I don't think many are or they are not recognized as such. Historic inbreeding results from uneven sampling from the population. This is most obvious with the males. The same few "popular" (well-promoted) individuals are used repeatedly, and many of the others are not used at all. The collection of genes from the latter may be lost to the population, particularly if it is small. Everyone becomes related to these popular sires and inbreeding becomes inevitable. What appears to happen is that slightly detrimental genes that individually might not make much of an impact start to accumulate in the population until breeders begin to notice that their litter sizes are smaller than they remember the old-timers reporting, they have difficulty getting a bitch pregnant and that various health problems seem to be turning up more often than in the past. Some may attribute these problems to diet, environmental toxins and the like, but the bulk of it is genetic [author's emphasis]. This is what inbreeding depression is all about.

Coefficient of inbreeding

The coefficient of inbreeding (COI) is the statistical probability that the two alleles at a randomly chosen gene locus are identical by descent; i.e., inherited from an ancestor common to both parents. The more inbred the breeding partners are, the more likely that they will share the same alleles. A common inbreeding paradigm in the dog world is the breeding of a grandfather to a granddaughter. Although this may be a general concept of dog breeders, it is contrary to how geneticists, especially population geneticists, think it should be done. If one ignores any previous inbreeding within the pedigree, the minimum COI of this breeding is 12.5 percent. Professional breeders of production animals such as cows, pigs, goats, horses, sheep and chickens, think that a COI around 9 percent is skirting the allowable limit. They, of course, are interested in such issues as health, productivity and reproductive viability. One then must ask what dog breeders are interested in? A COI of 12.5 percent means that it is very likely that the progeny of a granddaughter/grandfather cross share identical alleles at one out of every eight possible loci.

The steadily decreasing heterozygousity within the individual breeds is cause for alarm. Not only is there a loss of reproductive fitness, but other parameters such as longevity are also affected. A paper titled "Inbreeding and Longevity in the Domestic Dog," which was submitted by John Armstrong for publication in the Journal of Heredity, suggests that in the breeds he looked at, there is a decline in the median life span of about 7 percent for every 10 percent increase in inbreeding.⁹ Another example of the deleterious effects of inbreeding is what is happening to the immune system. More and more we are seeing such problems as autoimmune diseases, irritable bowel syndrome and various food and environmental allergies. The genes that control the immune system must be heterozygous if the individual is to have the ability to recognize foreign proteins, to differentiate foreign proteins from "self" and to fight off disease and parasites without overreacting to these "normal" environmental perils.

The genes that control the immune system are passed down together as haplotypes, one set from each parent. They are found so close together on the chromosome that very little if any recombination occurs. Recombination is the process of combining genotypes and phenotypes not present in either parent, but which show up in their offspring. When inbreeding occurs, the chance that a puppy will inherit an identical set of these genes from each parent increases. This, in effect, cuts the functional ability of the immune system in half and seriously compromises the quality and duration of life for the puppy. Those of you who have had a dog with allergies, with demodectic mange or without the ability to fight off a deadly disease know the tremendous suffering this involves, both for the dog and its owner.

There are other reasons for an impaired immune response, such as poor nutrition or a lack of vitamin E and selenium in the dam's diet (Fed Proc. 1979 Jun;38(7):2139-43. Influence of vitamin E and selenium on immune response mechanisms. Sheffy BE, Schultz RD.) Without those two nutrients the offspring are born without a sufficient number of immune competent cells. So there are environmental reasons for an impaired immune system, but the bulk of the literature suggests that inbreeding plays the greater role.

The rampant rabbit

Arguments against inbreeding are controversial in the dog fancy. Questions similar to the following are often asked: "Wild rabbits arrived in Australia in 1859, when Thomas Austin released 24 animals he had brought from England for sport hunting; why didn't the rabbit inbreed itself to death?"

This story is a good illustration of the problems associated with dog breeding. The first difference between dogs and rabbits is that the rabbits were not being selected for anything other than survival. They had the additional advantage of having an almost unlimited food supply, no effective predators and really no competition for their particular ecological niche. In fact, there was no natural selection to begin with because few if any diseases and parasites came with them. The breeding was as random as possible. The original rabbits had lots and lots of offspring, who also bred randomly, so the founder's alleles were comparatively evenly distributed during the first explosive phase of population growth.

Once the rabbit population was large enough to meet the Hardy-Weinberg criteria of about 10,000 to 100,000, the gene pool was pretty safe from genetic drift. The Hardy-Weinberg criteria states that the population needs to reach a certain number of individuals for it not to be subject to genetic drift.¹⁰ Considering that rabbits breed like, well, rabbits, they undoubtedly reached that population cushion fairly rapidly. On the other hand, certain dog breeds were intensively selectively bred right from the first generation and for criteria that had nothing to do with survival: In the Samoyed it was all-white coats, black lip lines and prick ears; thus, breeding was by no means random. In addition, because the population was never large enough early in the breed history to protect these dogs from genetic drift, the random loss of alleles was a serious problem. Loss of alleles that code for big brown spots does not matter in this breed, but what about those that control the immune response or allow an individual to metabolize an environmental toxin?

There are alternatives to inbreeding. Assortative mating is the selection for breeding of phenotypically similar individuals. For dog breeders this means that when choosing a mate for a bitch, you find a male that matches all the physical appearances or traits within the breed standard that you want to keep and that do not duplicate any of your bitch's faults.

Selection by phenotype is very common in those European countries where inbreeding is discouraged. According to M.W. Willis in Genetics of the Dog, most German breeds are bred with very little inbreeding--instead they use assortative mating and selection.¹¹ This results in a very uniform type among dogs appearing in the show ring. Assortative mating does increase the resemblance among littermates; however the difference between the two breeding techniques is that the chance of doubling up on hidden or undesired traits is minimized with assortative mating, even though the breeder is selecting the animals. This is not true of inbreeding.

Preserving genetic diversity

The optimal program for promoting genetic health involves breeders using assortative mating and avoiding inbreeding as much as possible in order to minimize the coefficient of inbreeding. Open the studbooks, and, if possible, use the original stock. This is just what was attempted with the Basenji. In 1987, two Americans, Jon Curby and Mike Work, embarked on a mission for their breed that would take them to Northeastern Zaire on a search for Basenjis in their native land. One by one they located dogs and bartered with their sometimes reluctant tribal owners, until seven African-born Basenjis were loaded for the trip home.

In order for their mission to be a success, however, the dogs had to be admitted into the studbook. The impetus for their mission was the existence of certain genetic health problems in the AKC Basenji that had become widespread due to the breed's limited gene pool. If these dogs could contribute their genome, it might be the answer to the breed's problems, but without pedigrees, little chance for AKC registration existed. Their best chance lay in a roundabout route, by trying to register the dogs with a foreign kennel club with less strict pedigree requirements, and then trying to register the dogs' descendents (after three generations) with the AKC. No guarantees existed as to whether the scheme would really work. It appeared the ability of these dogs to contribute to the AKC gene pool was uncertain, and at best, years in the future. In the end, perhaps they took the least likely yet most logical approach: A direct appeal to the AKC. The AKC approved the opening of the studbook to imports from this and a subsequent expedition, pending the approval of the Basenji Club of America, which was given in 1988.

Yet many questions remained. How would they deal with the fact that most of the imports were brindle patterned, a pattern not even allowed by their AKC standard? How would these dogs straight from the bush be accepted in American breeding programs? Would the influx of their genes sully their descendants and make them less competitive in the show ring? Recognizing that brindle was actually the most prevalent pattern in its native Africa, the Basenji Club of America amended its standard to allow brindle patterning, and many breeders soon considered their brindle Basenji's coloration a badge of pride. There was no compromise of quality--the top show Basenji, in fact the top hound in America for 1997, was a brindle Basenji. Most important of all, the new Basenji genes have so far proven to be free of the hereditary problems that had beset the breed.

Another way to maintain genetic diversity is to allow breeding between different strains of dogs that are really the same breed but that have had artificial breed status conferred upon them by the various registries. There have been numerous artificial breed splits along color lines or sizes or based on politics. One bitter dispute is between the American Kennel Club's Akita vs. the Federation Cynologique Internationale's Great Japanese Dog vs. the Japanese Kennel Club's Akita. There were never very many Akitas in Japan. Fewer still survived World War II. After its recognition of the Akita, the AKC closed the studbook on Akitas from Japan, effectively cutting the genetic pool of Akitas off from their land of origin.

The politics innate in the registries have not followed rational genetic lines but rather have been subject to the demands of power, influence and winning kennels. Basenji and Saluki breeders understand firsthand what we mean by politically restricted gene pools subordinated to a European concept of purebred dogs. These two breeds of great antiquity are not AKC-recognized unless they come from just a few founders. It matters not that they have been around for several thousands of years and are still numerous in their lands of origin.

Hiding genetic disease

If breeders withhold information about the genetic disease in their breed or within their line, then we face an insurmountable barrier in any attempt to control those diseases. Open discussion about problems your dogs have produced allows other breeders to make more informed choices. Secrecy and denial only perpetuate the problem. Genetic testing may help; however, if the disease does not appear until late in the dog's life, then only by alerting your puppy owners "downstream" from the affected dog can you hope to prevent further misery for both the dogs and owners.

False pedigrees, absent genetic testing, can invalidate the conclusions drawn from pedigree analysis. We recognize that there is some "noise" (false information) in the various registries and, in some cases, a significant level of noise. This makes pedigree analysis difficult and in some cases impossible. The SCC (French Kennel Club) has done random paternity and maternity checks on about 200 pups from recent litters from various breeds. The parents of 17 percent of the pups as indicated by the pedigree were incorrect. We suspect that this French example is not only a French example, but a worldwide example. This may occur even more often in the United States where there is a significant amount of money changing hands between commercial breeders and pet stores. This quote from C.A. Sharp, author of "The Biggest Problem," in the Summer 2000 edition of Double Helix Network News, says it all succinctly:¹²

You all know them. The ones that put winning above all other goals. "It doesn't matter as long as the dog wins," is their mantra. Their dogs must win, as must their dogs' offspring, and woe betide anyone who stands in their way as they pursue greater breed and personal glory... If a genetic problem isn't apparent they will ignore it. If it can be (surgically) fixed they will. If it can't, they will employ some variant on "shoot, shovel and shut-up," or recoup their losses by shipping the dog a long ways away, preferably across an ocean or two. If someone else knows about the problem, the Incorrigibles will use any means at their disposal to shut that person up, ranging from veiled threats and rumor-mongering to blatant bully tactics and threatened legal action.

Most of us can think of an example of this behavior. Amongst Samoyeds it was the attack on Rosemary Jones, the breeder who first brought the dirty little secret of progressive retinal atrophy into the light of day and who named names and published pedigrees. Without acknowledging there is a problem, how can we fix it? Why is it also that we speak among ourselves about these unethical breeders and yet we do business with them because... their dogs win! What does this say about our own ethics? The form of PRA expressed in Siberian Huskies and Samoyeds is an X-linked, late-onset disease that usually appears somewhere between 3 and 5 years of age. By testing breeding stock, breeders will be able to avoid producing affected offspring. Research on the disease was done at the James Baker Institute, Cornell University and was funded by a combined grant from the AKC Canine Health Foundation and the Siberian Husky Club of America. The test is offered by Optigen®, LLC (www.optigen.com).

Let's move on to the Ostrich Syndrome breeders. These are those among us who will do anything not to test for a genetic disease. If they do not test, they will never find it. Denial is the name of that game. Those of us who are truly dedicated to the health of our canine companions will not make any headway until we first recognize and confront the human behavior expressed when faced with canine genetic disease. One can conclude that the genetic problems in purebred dogs are not intrinsically a canine problem, but rather a human problem supported by politics, old wives' tales, ignorance and even outright rejection of scientific opinion.

To conclude, Basenjis are far from being the only breed to suffer from genetic health problems caused in great part by small gene pools. Purebred dogs have gained the reputation as genetic disasters. Many breeds count fewer than 50 dogs as their foundation stock - a number that would send shudders up the spine of any wildlife biologist seeking to save an endangered species. Breeding schemes for endangered species focus on increasing the gene pool as much as possible by integrating all available animals. In many of our breeds of dogs, the gene pool is out there - we just can't jump in because of the policies of our registries and clubs.

Chapter 5
The Shallow End of the Gene Pool

The ability to go back to stock from a breed's country of origin (COO) in order to expand the gene pool is a process known as introgression. The basic tenants of the AKC make such a process difficult to impossible for dogs originating in most "non-western" societies unless special exceptions are made. Many COO dogs come from countries in which registries do not exist or do not meet the AKC's specific standards. In the early development of many breeds, the AKC often facilitated expansion of the gene pool. Most recent attempts to introduce new genetic material by the registration of COO stock have met with the AKC's steadfast position that unregistered stock cannot be directly integrated into the studbook. The AKC will sometimes make exceptions in the face of compelling health or medical reasons. In such cases the parent breed club must vote in favor of such a step and then petition the AKC to open the studbook for a brief time. The Saluki, for example, is an ancient breed that still exists throughout its native Middle East. Its Bedouin owners can recite its pedigree for generations, but such is not acceptable proof of purity for the purposes of AKC registration. The AKC Saluki is derived in most part from a small number of founding dogs brought to England around the 1920s. In 1945, two Salukis bred by King Ibn Saud came to this country and after some persuasion, the AKC made a special ruling whereby descendants removed by three generations from these imports could be registered, as long as the generations in between were always bred to registered stock. Today, imported COO Salukis are formidable competitors in coursing trials. Attempts to gain AKC recognition for these dogs, however, have been unsuccessful, largely because of a lack of consensus by the parent club as well as the lack of any overwhelming genetic problems that would lend urgency to the matter.

In the cross fire

In some breeds, no COO stock exists, or that which does exist shares the same problems as the AKC stock. In such cases, crosses to other breeds may be the only way to introduce new genes. Early in the creation of breeds, such crosses were commonplace. For example, although the Shih Tzu is an ancient breed, at the beginning of this century the breed is thought to have become extinct in China. Modern Shih Tzu descend from seven dogs and seven bitches, one of which was not a Shih Tzu, but a Pekingese. This cross occurred in 1952, long before AKC recognition of the breed. While the early registration bodies sometimes sanctioned crosses to other breeds, after a breed was established, they allowed crosses only in the rarest of circumstances.

The Dalmatian is a breed with a genetic predisposition for abnormal uric acid metabolism that leads to painful and debilitating stone formation. In 1988, at the behest of the board of directors of the Dalmatian parent club, and with the approval of the AKC, a cross was made to a Pointer in an attempt to introduce the genes for normal uric acid metabolism into the Dalmatian genome. The plan was to breed the normal progeny of this initial cross back to Dalmatians, continuing for many generations until their descendents were essentially Dalmatians with no trace of Pointer (except for the normal uric acid metabolism). With each backcross (crossing the mixed progeny back to pure Dalmatians,) the proportion of Pointer chromosomes would decrease by one half. This is a common plan for the introduction of a new gene into another population, although several factors can slow or halt its progress. These factors include linkage wherein the trait being selected for is on the same chromosome as other traits that may be essential for type. If, for example, the trait for normal uric acid metabolism was on the same chromosome as the trait for patches, acceptable in Pointers but not in Dals, a decision for health would also be a decision against type. Even so, in time, the Pointer derived chromosome bearing the introduced allele will cross over and exchange genetic material with its homologous Dalmatian derived chromosome and hopefully breed true for the Dalmatian type without the metabolic defect.

This did not happen, though. The descendants with normal uric acid metabolism tended to have ticking, instead of spotting, suggesting the possibility of either linkage or pleiotropic effects. Rember that pleiotropic effects are those where one gene causes several diverse effects. Further problems arose with a change in consensus about the project within the Dalmatian Club of America. The club subsequently objected to the registration of the crossbred progeny and lifted the registration privileges for these dogs. Thus, although the experiment was a medical success, it was not successful from the viewpoint of maintaining Dalmatian type or achieving widespread acceptance. The important lesson in this case, however, is not that the venture failed, but that the AKC had the foresight to approve it in the first place. Perhaps the most important lesson was one of requiring full consensus of all parent club members before undertaking a project of this nature--"full consensus" implies unanimous, which is impossible in most clubs. The AKC now requires a full membership vote from the parent club before granting approval.

One of the rarest breeds in America is the Wirehaired Pointing Griffon. In the 1980's, the breed's limited gene pool resulted in the decision by some breeders to cross the breed with the Cesky Fousek, a European breed. Griffon breeders did not universally approve the project and the AKC did not grant recognition to the resultant dogs. Breeders have the liberty of choosing the direction of their own breeding programs. If they choose to cross their dogs to another breed without a priori parent club and AKC approval, they cannot expect AKC recognition of their stock--no matter how good their intentions.

While it is clear that in some cases the AKC will consider "breaking the rules" in order to promote genetic health and diversity, no set guidelines seem to exist by which a parent club can petition for such an exception. Shouldn't a published set of criteria be available so that breed clubs know at what point they may reasonably resort to this step? Should the breed club or the AKC be the final authority when deciding if such exceptions are to be made?

It is the parent breed clubs that initially develop breed standards, maintain stud books, and petition AKC for recognition of the breed and the club. Even after agreeing upon a standard, the parent club may consider amendments to it and, if deemed appropriate, change it. In developing a standard, a parent club exerts tremendous power over the genetic future of a breed. In some cases, standards require physical characteristics that are inconsistent with hardiness. For example, brachycephalic features predispose a dog to breathing difficulties, diamond shaped eyes to entropion and/or ectropion, excessive wrinkling to moist dermatitis, and excessive size coupled with deep chests to gastric torsion (bloat). In most of these cases, the breed standards were drawn up long before the association of the traits with physical difficulties was known. Such traits have become so ingrained as basic to breed type that breeders and parent clubs choose to retain them despite their associated problems. Since the parent club has sole discretion over the breed standard, only the breed club can effect a change in the standard to change the essence of type and reward healthier, but less traditionally typey, specimens. In almost every case in which type has been at odds with health, parent clubs have chosen to give type precedence. The results are obvious!

Breed standard disqualifying faults also affect the genetic health of a breed. The AKC has several disqualifying faults applicable to all breeds; perhaps the best known of them is unilateral or bilateral cryptorchidism--the failure of one or both of the testicles to descend normally into the scrotum. Since this fault is less detrimental to health than a plethora of other far more serious faults with far greater heritability, the universal disqualification of such dogs is of questionable value to any breed. Several parent clubs impose further disqualifications, usually for traits considered extremely untypical for the breed. Common disqualifying faults are for dogs over or under a certain weight or height, for different eye color, or coat colors or types. Dogs with disqualifying traits cannot be judged at a conformation show, but may compete in other venues. By banning these dogs from conformation competition, parent clubs hope to discourage breeding from them and perpetuating the offensive trait. Removal of dogs from the breeding population based upon arbitrary aesthetics can do more harm than help, especially in cases where the breed has a limited gene pool and the banned trait has no strong hereditary component.

Lack of appreciation of genetic aspects of a trait can result in illogical and detrimental disqualifications. One example is the Mantle (also know in the USA as the "Boston") Great Dane. These dogs are black with typical "Irish marked" coat pattern, that is: white feet, tail tip, muzzle, and collar, just like the typical pattern of the Boston Terrier. This color pattern was, until recently, listed as a disqualifying fault under the AKC standard for the breed. Yet serious breeders of Harlequin Great Danes have routinely used the Mantle in their breeding programs. Breeding a Harlequin to another Harlequin statistically results in 25% Harlequins, 25% merle (disqualified), 25% white (disqualified and commonly defective) and 25% Mantle (until recently also disqualified). This gives a predicted percentage of show marks of no more than 50% (some further losses may occur from unsuitable markings on Harlequins and Mantles). Breeding a Harlequin to a Mantle, however, results on average in 25% Harlequin, 50% Mantle, and 25% merle; with potentially 75% show marks produced in this breeding. Thus, a substantial proportion of dogs produced from the traditional breeding of Harlequin to Harlequin--perfectly acceptable colored parents--will be disqualified from breed competition by virtue of the combination of acceptable genes that together produce an unacceptable color pattern in this breed. Some of these disqualified dogs may be of such high quality otherwise that they are sought after for breeding back to Harlequins.

Before the introduction of the Mantle this was often the case as their use as a breeding partner to a Harlequin, as noted above, actually results in a greater percentage of acceptably colored offspring than would a Harlequin to Harlequin breeding. It also avoids the production of potentially defective homozygous merle dogs, known as white Danes. Unfortunately, because these Mantles were disqualified from competition, their quality, until recently, could not be objectively judged by way of conformation awards or titles. It was obvious to many that the standard with these disqualifications was counterproductive. Finally, in 1996, in recognition of the importance of the Mantle Dane to the breeding of Harlequins, the Great Dane Club of America voted to change the breed standard to accept the Mantle Dane as an acceptable color. Changing the standard is one of the heaviest responsibilities that a parent club can undertake, and to do so in recognition of genetic mechanisms is a progressive step for a parent club. Unfortunately, not all clubs have shown such an ability to accept genetics over tradition.

In other breeds, disqualifications have been implemented in recognition of health problems related to certain traits. In 1979, a "white" Doberman Pinscher named Sheba was AKC registered. She was undeniably eye-catching, with a light cream coat, translucent blue eyes, and pink nose and eye rims. Her offspring were crossed to each and produced more such dogs. These striking animals aroused much interest, but were apparently tyrosinase positive albinos. Not only were these dogs considered untypical for the breed, but because albinism can be associated with health problems, especially those from ultraviolet exposure, the Doberman Pinscher Club of America acted not only to disqualify these dogs, but worked with the AKC to develop a scheme whereby dogs possibly carrying the gene for albinism could be identified by their registration numbers. Such dogs are identified with a "Z" as part of the litter or individual registration, the Club having acted proactively to limit this problem - a very postive move.

In recent years, most parent clubs have formed breed health committees, the success of which depends upon many factors. Some clubs have a large membership from which to draw and an open door policy which has brought in a diversity of educated and dedicated committee members. But some clubs still operate under closed memberships, in which prospective members must be sponsored by existing members and voted upon by the full membership. These clubs have been less apt to deal with health issues while preferring to preserve the status quo. Political issues, of course, are rampant within any breed, and control of the parent club means control of the breed standard--and ultimately the future of the breed. Thus, in certain breed clubs, because of either small breed numbers or exclusionary practices, the chance of forming a strong health committee is considerably lower than in those clubs with a more diverse membership.

The first step a breed health committee faces is identification of health problems. This step is not as simple as it may seem. Breeders may have a "feeling" about what may be a problem based upon personal experience and anecdotal reports. The problem then becomes one of determining whether these problems are breed specific or common to all breeds. For example, if a breeder knows of ten dogs over the past three years that suddenly fell over dead at a young age, this might raise some suspicion that the breed had a problem. But perhaps this is no more than would be seen in any breed of dog. The problem is that 95% of that breeder's contacts also have the same breed of dog; it would be very unlikely that the breeder would ever hear about the same circumstance in another breed simply because of lack of communication. Thus, a major problem in breed specific health surveys is one of bias.

While it is unrealistic to expect parent clubs to have the expertise conduct statistically sound and unbiased health surveys, they are being forced to shoulder this responsibility. Some have done a better job of tackling it than others. The greatest barrier to parent club health surveys is lack of trust on the part of breeders, since those collecting the information are often that breeder's competitors. Though hiding health information may seem petty and dishonest, recall that many breeders have a lifetime of hard work, study, money, and emotion invested in their line of dogs. They fear that if they are the only ones to come forward with information, they may be the only ones branded as having unhealthy dogs, effectively terminating the line to which they have devoted their lives. In popular breeds much of the information thus comes from individual pet owners. In some other breeds efforts are undertaken to ensure anonymity.

For example, the Salukis In Good Health Committee developed a process in which identifying information and medical information pertaining to a dog are sent in separate sealed envelopes, coded by a "middle-man", and sent on to separate data entry people so that no person ever sees the medical and identifying information together. Only in the final step are the two sets of information associated within a third database that encrypts the information so that actual identification of animals is still inaccessible to committee members. It is this information that is ultimately used for performing analyses.

Code of ethics

Most parent breed clubs maintain a standing ethics committee to develop, maintain and enforce some form of code of ethics. Such codes are known by various names such as Guidelines for Responsible Ownership, Guidelines for Breeders, Guidelines for Ethical Conduct, Ethical Guidelines, Mandatory Practices, Principles of Integrity, Statement of Conduct, Canon of Ethics, Breeders Code and Code of Recommended Practices. There are several more variations upon this theme, but in general, the parent clubs' codes of ethics make vague and not very binding statements about genetic health, ranging from no mention at all, to actually listing the diseases of interest and the screening required.

Some parent clubs have had serious internal political problems when establishing a standing ethics committee, with the result being that some clubs have yet to progress this far. Other clubs have official committees, but they are kept out of sight and out of mind. In some clubs, because of the personalities and beliefs of some of the more successful members, those individuals have severely controlled or thwarted the actions of such committees. When one of the more successful breeders with more champions bred and shown refuses to screen for hip dysplasia, the club is often powerless to enforce screening requirements. In such cases, genetic screening becomes "recommended," "encouraged" or "should be considered."

There are several breed clubs that do in fact list the screening that should be done and say that such screening is mandatory under the code of ethics. A number of codes of ethics mention the Orthopedic Foundation for Animals (OFA), but no other registry such as the Canine Eye Registration Foundation (CERF). This is a step in the right direction, but one finds virtually no evidence that anything has been done to discipline or terminate membership of any successful breeder who fails to follow the club's screening regimen. In fairness to breed clubs, it is difficult in a litigious society to attempt to force any sort of genetic testing without that attempt resulting in internal lawsuits. If changing a breed standard to add a comma to correct punctuation is difficult, think of how difficult it might be to establish a genetics committee to interface with an ethics committee and develop a genetic screening regimen appropriate to the breed. Imagine the legal tests when a successful breeder is censored by some means for not conducting such screening.

The answer lies in educating the club membership. Advertisements of top dogs need to include the genetic screening supporting them. Articles need to be frequently published in the club and breed magazines/newsletters questioning the folly of purchasing a dog from anyone that did not have an effective genetic screening regimen. In our democracy, the free market exerts the force for change that is otherwise prevented by the costs of litigation. The puppy buying public is slowly becoming aware of the problems of genetically inferior dogs. States are rushing to enact puppy lemon laws.

To some, the AKC is becoming known as the registry of sick dogs. Any breed club's attempt to rise above the mire will serve to differentiate that breed from the "You don't want one of those, they have a lot of health problems." Individual breeders can enhance the desirability of their puppies by documenting generations of genetically healthy dogs.

Sample codes of ethics

Following are representative extracts from a sample of various breed clubs codes of ethics:

Akita "I will keep well informed in the field of genetics and work to eliminate hereditary defects from the breed... I will participate in a program of hip x-raying and eye examinations by qualified veterinarians to eliminate hip dysplasia and congenital eye problems. When an Akita has hereditary faults of such nature as to make his or her use for breeding detrimental to the furtherance of the breed, that dog shall be neutered/spayed."

Basenji "Ethical breeders should discuss openly and honestly the genetic and physical problems that have occurred in their lines. This should include the potential of these problems to be passed on, especially in cases where testing can indicate only that a dog is currently free of a problem, but cannot determine that the problem or the ability to pass it on will not be inherited. Stud dogs or brood bitches who produce offspring of consistently poor quality or with genetic problems known to be inherited in the breed are therefore of no value as breeding stock and should not be used again."

Basset Hounds "Breedings will be directed toward producing Basset Hounds of exceptional quality in breed temperament, Basset Hound type and ability to hunt game. Only healthy and mature dogs and bitches free of congenital defects and of characteristic breed type, sound structure and temperament shall be bred."

Borzoi "No animal selected for breeding should have any serious hereditary defects as determined visually and by veterinary examination."

Chesapeake Bay Retriever "Be aware of genetic defects which can be harmful to the breed. When breeding, endeavor to select animals that will reduce the incidence of genetic problems while enhancing the positive attributes and abilities of the breed. Be open with all persons interested in the welfare of the Chesapeake Bay Retriever and discuss possible physical or temperament defects in your own stock."

Dachshund no statement concerning genetic fitness for breeding.

Doberman Pinscher "Stud dogs should not be bred prior to one (1) year of age and should be in good health and free from communicable diseases and disqualifying faults." ... Any bitch accepted for stud service should be at least 18 months of age, in good health and free from communicable diseases and disqualifying faults."

English Cocker Spaniels no standing ethics committee. Statement of Conduct is silent on genetic health.

Field Spaniels "Breed only healthy and mature animals who are free from serious congenital and hereditary defects."

Golden Retrievers "Owners of breeding animals shall provide appropriate documentation to all concerned regarding the health of dogs involved in a breeding or sale, including reports of examinations such as those applying to hips and eyes. If any such examinations have not been performed on a dog, this should be stated."

"Animals selected for breeding should:

(i) be of temperament typical of the Golden Retriever breed; stable, friendly, trainable, and willing to work. Temperament is of utmost importance to the breed and must never be neglected;
(ii) be in good health, including freedom from communicable disease;
(iii) possess the following examination reports in order to verify status concerning possible hip dysplasia, hereditary eye or cardiovascular disease.

Hips: appropriate report from Orthopedic Foundation for Animals; PennHip; Ontario Veterinary College; BVA/KC Hip Score (Great Britain) or at least a written report from a board-certified veterinary radiologist (Diplomat of the American College of Veterinary Radiologists).

Eyes: appropriate report from a Diplomat of the American College of Veterinary Ophthalmology (ACVO), or from a BVA/KC approved ophthalmologist (Great Britain).

Hearts: appropriate report from a Diplomat of the American College of Veterinary Medicine, Cardiology Specialty.

Consideration should be given also to other disorders that may have a genetic component, including, but not limited to epilepsy, hypothyroidism, skin disorders (allergies), and orthopedic disorders such as elbow dysplasia and steochondritis."

German Shepherd Dog no statement of genetic health in the Breeders' Guide.

German Wirehaired Pointer "Only those dogs free of recognized genetic defects shall be used in a breeding program."

Italian Greyhound "It is not always possible to prevent the occurrence of inherited diseases, as there are not yet definitive tests to identify carriers of genetic diseases. A breeder's obligation with regard to genetic diseases is to make every effort to prevent their occurrence and to share openly and honestly all information available regarding the genetic health status of his/her dogs. While elimination of genetic diseases is a worthy goal, the converse is that excessive culling of animals from the gene pool may have the equally deleterious effect of limiting the gene pool in the breed. Breeders should be cautious about removing animals from the breeding pool solely because they are distantly related to an affected individual."

Irish Setter "Make every effort to learn about the structure, anatomy, action, behavior and other inheritable traits of the Irish Setter. To use this information to adhere to the breed standard and produce sound, healthy dogs with good temperament... To use or give service only to registered stock that is believed to be free of serious abnormalities which are considered inheritable... When selling an Irish Setter known to manifest hereditary defects considered to be detrimental to the breed, use written contracts or spay/neuter agreements to prevent the dog from being bred."

Miniature Pinscher "Breed only mature animals in good health, free from communicable diseases and major genetic faults."

Pekingese no mention of genetic health in Code of Ethics.

Pointer "Only animals of quality with characteristic type, sound structure and temperament, and free of congenital faults should be bred."

Pugs no mention of genetic health in Code of Ethics.

Rhodesian Ridgebacks "Only dogs screened and certified clear of hip dysplasia shall be bred. Breeders are encouraged to screen for all appropriate hereditary disorders."

Rottweilers "Breed only AKC registered dogs and bitches which have OFA certified hips (or HD-free hips as certified by foreign counterparts of the OFA). Imported Rottweilers must have OFA hip certification within six months after arrival in U.S.A. If semen is used from an imported Rottweiler, the dog must be x-rayed and certified by the OFA or foreign counterpart at no less than 24 months of age. Breed only dogs and bitches of stable temperament with no disqualifying physical faults according to the AKC Rottweiler Standard (i.e. entropion, ectropion, overshot, undershot, wry mouth, two or more missing teeth, unilateral cryptorchid or cryptorchid males, long coat, any base color other than black, absence of all markings.) Offer at stud with a signed written contract, only mature (two years of age or older) healthy dogs with OFA certified normal hips, free of communicable diseases, having none of the faults listed in Section 2 above. Refuse stud service to any bitch not meeting the same requirements. Breed only bitches two years of age or older with OFA certified normal hips, in good health, free of communicable diseases, having none of the faults listed above in Section 2, to not more than one stud dog at any one season, and not more than two out of three consecutive seasons. Plan all litters with the goal of improving the breed."

Saluki "To protect every Saluki from the suffering of genetic diseases, affected individuals will not be bred from."

Samoyed "Each litter is the result of conscientious planning, including consideration of the parents' freedom from hereditary defects, type, soundness, temperament and general conformance to the official standard of the breed. The SCA member must be particularly concerned with the proper placement of puppies, both pet and show potential. The SCA member only breeds healthy, mature Samoyed adults, preferable 24 months of age, but at least 18 months of age. Prior to breeding any Samoyed, the SCA member obtains certification that its hips are normal from the Orthopedic Foundation for Animals, an equivalent foreign registry, or from a board approved radiologist and has its eyes certified free from genetically transmitted defects by a certified Veterinary Ophthalmologist. The SCA member knowingly breeds Samoyeds only to other registered Samoyeds."

Scottish Deerhounds "Breeders are urged to breed only dogs and bitches that are in good health and of such maturity (yet not past their prime) to demonstrate a degree of freedom from genetic defects breeders are urged to test for health defects, where possible."

Shih Tzu "In my breeding program I will keep alert for and work to control and/or eradicate inherited problems and conditions that are particular to my breed, and breed as closely to the standard of the breed."

Silky Terriers "All breeding stock should be of sound temperament, free from congenital defects such as blindness, deafness and dysplasia. Dysplasia of the hips and shoulders may be ascertained by x-rays taken and read by a veterinarian who is familiar with the proper procedure and diagnosis."

Visla "Breed only those dogs who are free of serious hereditary defects including epilepsy, progressive retinal atrophy, von Willebrands, entropian and cranial muscular atrophy and who are over two years of age and have been xrayed and OFA certified as free from hip dysplasia."

Weimeraner "Choose only healthy parents of good temperament and qualities in relation to the Weimaraner's AKC-approved official standard, and whose hips have been X-rayed and certified free from hip dysplasia by either the Orthopedic Foundation for Animals (OFA) or any ABVR certified veterinarian. Not use dogs with hereditary defects or disqualifying faults for breeding."

Yorkshire Terriers "Prior to breeding, owners of stud dogs and bitches will adequately screen for both infectious and hereditary diseases, using current techniques as well as those developed in the future."

Money for research

The development of genetic tests is an expensive and time-consuming process. Often the same disease in two distinct breeds is the result of a different mutation. This requires a separate test for each breed. With the advent of the AKC Canine Health Foundation (include a URL here), individual clubs are able to raise money for genetic research and have that money matched by grants from the foundation. Other benefits of using the AKC/CHF are: Their ability to screen and evaluate research proposals, locate qualified research facilities, supervise and assess on-going research projects, and prevent the duplication of management and administrative functions, thus saving time and money.

Even more important than money is the raw material needed to conduct the research. This is where the individual breeders and breed clubs can make a most necessary and invaluable contribution. Without blood or cheek swab DNA samples, accompanied by accurate and appropriate pedigrees, genetic research cannot continue to advance. With this information, tests can be developed so that breeders will have the tools to make informed and responsible breeding decisions, and rectify some of the extensive health problems our dogs suffer.

It is strongly suggested that breed clubs look at the heritable diseases associated with their breeds, and establish a well-defined screening protocol mandatory for all dogs owned or bred by members of the club. The AKC Canine Health Foundation is there to help you. Furthermore, it is recommended that the code of ethics include a statement to the effect: "Members, when advertising any dog, bitch or puppy, in any venue, will include in that advertisement the genetic screening conducted on that animal and its parents." Such mandates are within the prerogative of breed clubs, and only they have the power to correct the current appalling situation of poor genetic health. It is time to stop bashing the AKC - "we are them and they are us." The responsibility for requiring genetic screening rests squarely with the parent clubs.

Chapter 6
Cancer, Immune Problems And Vaccinations

According to the AKC figures, the incidence of cancer in the purebred dog is epidemic. Why is this so? Due to advances in veterinary healthcare, many dogs are living to an age where cancer is more likely to appear. We are also living in a polluted environment. Our canine companions are at an even higher risk for exposure to environmental toxins. Not only do some of us load our dogs up with flea and tick collars and dips, but their grooming habits make it much more likely they will ingest pesticides and other chemical carcinogens. One ubiquitous carcinogen is found in the outgassing of asphalt on hot days. It is also seen in meat that has been charcoal broiled. The chemical name for this substance is benzo [o] pyrene, and dogs simply crossing the street can get it on their paws and later lick it off. This chemical does its dirty work by causing missense mutations, a type of mutation that causes the replacement of a different amino acid in a protein and that can result in cancer.

At a recent conference, hosted in part by the AKC, it was revealed that cancer is the leading cause of death in dogs, after euthanasia. Lymphomas are the most common cancer found in canines, comprising about 20% of all malignancies. In humans, this type of cancer has been associated with chromosomal anomalies, it is most likely that this will prove to be true for dogs as well. What must be emphasized is that all cancers have a genetic component. We know that there are familial and breed related cancers and that only emphasizes the genetic aspects of the disease. Identification of affected families within the canine population may lead to the discovery of cancer susceptibility genes. It is no surprise to learn that those breeds with very small foundation numbers and those breeds with an overabundance of popular sires are those most valuable for this study.

The Genetics of Cancer

Two classes of genes are suspected of being involved in the occurrence of cancer when they are mutated: Tumor-suppressing genes and proto-oncogenes, genes that function to encourage and promote normal growth and division of cells. The progression of tumor growth correlates with mutations that activate oncogenes (mutated proto-oncogenes) and render tumor-suppressor genes inactive. These mutations somehow "uncouple" the same mechanisms that allow normal cell division. What is so frustrating for both researchers and clinicians alike is that different combinations of mutations are found in different types of cancer and even in cancers of supposedly the same type in different patients. This reflects the random nature of these mutations.

Cancers caused by these loss-of-function mutations are more likely to be inherited. Parents that pass on a mutation in one copy of the gene produce offspring with a predisposition for cancer in that the disease requires only one mutation in the remaining "good" copy of the gene to be expressed.

Another familial type of cancer predisposition would be those that involve DNA repair. The body has mechanisms in place to detect errors in duplicated DNA. If mutations occur in the genes that code for the proteins responsible for this repair process, bad copies of the cellular DNA will accumulate. The initiation of cancer requires multiple events, which is perhaps one of the reasons cancer is seen more often as we age. The first mutation that is not repaired is thus inherited by any subsequent daughter cells. Cells thus affected do not undergo apoptosis--cellular suicide--and are rendered immortal. (both definitions are fine) Even though immortalization is not the same as carcinogenisis, which is the generation of cancer from normal cells, most transformed cell lines do not die after their normal number of cell divisions. This is a requirement for the further development of malignancies.

There appear to be several stages in the development of tumors. First, there is an initiation phase, in which an optimum or threshold level of mutations occurs and "tips the scales" toward tumor genesis. Once the cell has been transformed, there is a latent stage, in which mutations that have a selection advantage start to proliferate. During the clinical phase, the tumor becomes large enough to induce symptoms. These symptoms are caused by tissue destruction, or the production of soluble factors that can be detected in the blood or the tumor can depress vital functions and act as a space-occupying lesion in a confined anatomical space.

Genetic mistakes initiate cancer

Since apoptosis is also under genetic control, it is not surprising that many of the proto-oncogenes and tumor-suppressor genes altered during apoptosis are those genes involved with cell death. Many proto-oncogenes code for proteins involved in mechanisms that regulate the social behavior of cells. Signals from those cells in the immediate environment induce their neighbors to divide, differentiate and even undergo apoptosis. It also appears that both types of genes are involved with or expressed during the control points of the cell cycle. Human cancer studies show that mutations in the tumor suppressor gene called p53 account for many tumors. One of the functions of this gene is that it normally prevents cells with damaged DNA from proceeding through the cell cycle. The presence of the protein product encoded by p53 induces the expression of the waf-1 gene. The waf-1 gene produces a protein that normally inhibits the activity of several similar cellular proteins called kinases (enzymes that catalyze the conversion of proenzymes to active enzymes) that are involved in stopping cell cycle progression. A mutation in either the p53 or waf-1 gene sometimes can cause the loss of that "emergency brake" function and allow uncontrolled growth. One recent study has linked a case of benign canine melanoma to loss of this function. However, loss of apoptosis isn't the only culprit that causes cancer.

Many types of genetic mishaps can occur and can lead to disease. The basic types of genetic accidents include point mutations, deletions and chromosomal translocations mentioned earlier. The insertion of mobile genetic elements such as transposons--segments of DNA that are capable of moving to a new position within the same or another chromosome--or retroviral DNA-- retroviruses are potent disease agents with the capability of incorporating their DNA into the host cell's DNA--into the cell's genetic material are two other types of mutations.

Malignant transformations occur for a variety of reasons. Oncogenes, exposure to chemical carcinogens and ionizing radiation such as X-rays all play a role in inducing neoplasias. We even can "catch" cancer. In a number of species, although not yet demonstrated in dogs, retroviruses have been proved to be the cause of a variety of different diseases, including cancer.

A virus does not have the ability to reproduce itself but instead hijacks the host cell's reproductive capability by inserting its own DNA into the genome of the cell it has infected. It then forces that cell to produce the proteins it needs. This can cause something called an insertional mutation. Depending on where it inserts its viral DNA, the mutation can wreak havoc in a variety of ways. The result of these genetic accidents can alter the gene sequence so that it produces a protein with abnormal activity or even no activity at all.

Free radicals can attack DNA

Outside influences also can lead to mutations and changes in cellular genetics. Because we breathe an atmosphere that contains oxygen and we digest food, our bodies are constantly producing free radicals--highly reactive oxygen molecules that occur naturally in the body because of metabolic processes. Environmental factors such as air pollution, radiation, pesticides, herbicides, many drugs and cigarette smoke react within the body to cause free radical production. These molecules can damage DNA, affect the structure and function of cell membranes and damage certain regions of proteins that have enzymatic functions. Older humans and animals are more at risk due in part to increased levels of free radicals as well as an impaired ability of the immune system to eliminate altered cells. Very inbred dogs also have weakened immune function. (http://cc.ysu.edu/~helorime/inbrimmune.html)

Autoimmunity & Vaccinations

Autoimmune disease is genetic but like many other polygenic diseases, there is an environmental component. In the case of thyroiditis and diabetes, there is an established link to environmental triggers. Why are we seeing a rise in such diseases in the purebred dog? One could suggest it might be poor and outmoded breeding practices, i.e, inbreeding referred to as line breeding by many dog breeders. The portion of the genome that codes for the genes that help us recognize "self" is called the MHC--the Major Histocompatability Complex. These genes are located very close to each other and therefore it is very rare for recombination to occur. This in effect means that the genes from each parent are inherited intact as haplotypes. If the parents are closely related, then the possibility exists that they share the same genes at that site, i.e., they are homozygous by decent. This essentially cuts the functionality of the immune response in half- not a good thing. Normally, autoimmune diseases can be separated into diseases that are "organ-specific" and "systemic" categories. For instance, an organ specific example would be Graves' disease that is characterized by the production of antibodies to the thyroid-stimulating hormone (TSH) receptor in the thyroid gland. In the case of Hashimoto's, thyroiditis antibodies are formed against thyroid peroxidase; and in type I diabetes (the type most often seen in dogs) by anti-insulin antibodies. An example of a systemic autoimmune disease would be SLE (systemic lupus erythematosus). It also appears that some individuals are more at risk than others of developing particular diseases. As mentioned before, susceptibility to autoimmune disease is controlled by environmental and genetic factors, especially MHC genes. Results from both twin and family studies show an important role for both inherited and environmental factors in the induction of autoimmune disease. In addition to this evidence from humans, certain inbred mouse strains have an almost uniform susceptibility to particular spontaneous or experimentally induced autoimmune diseases, whereas other strains do not. These findings have led to an extensive search for genes that determine susceptibility to autoimmune disease.

One way of determining this in humans is to study the families of affected patients; it has been shown that two siblings affected with the same autoimmune disease are far more likely than expected to share the same MHC haplotypes. The more closely related two individuals are, the more likely that they share the same haplotype. The association of MHC genotype with autoimmune disease is not surprising, because autoimmune responses involve T cells, and the ability of T cells to respond to a particular antigen depends on MHC genotype. It appears that susceptibility to an autoimmune disease is determined by differences in the ability of variations of the MHC haplotypes to present various proteins that mimic "self" to those T cells that react to them. Inbred animals have fewer allelic variants. An alternative hypothesis for the association between MHC genotype and susceptibility to autoimmune diseases emphasizes the role of MHC alleles in controlling the variety of T-cell receptors. This lack of diversity means that developing and immature immune cells that are specific for particular self-antigens are not selected against and so are allowed to reproduce themselves.

However, MHC genotype alone does not determine genetic susceptibility to disease. Identical twins, sharing all of their genes, are far more likely to develop the same autoimmune disease than MHC-identical siblings, demonstrating that genetic factors, other than the MHC also affects whether an individual develops disease. One of these genetic factors would be B or T cell immunodeficiencies. Symptoms of this condition include eczema, dermatitis, heart disease, inhalant and food allergies and neurological disease. These conditions are often seen in the purebred dog.

This however begs the question as to why we are seeing a rise in autoimmunity associated with vaccinations. J Autoimmun. 2000 Feb;14(1):1-10. Vaccination and autoimmunity-'vaccinosis': a dangerous liaison? Shoenfeld Y, Aron-Maor A.

The whole duration of immunity and the timing and necessity for various vaccinations are being questioned. Many veterinary training schools are changing their recommended vaccination protocols. The practice of annual vaccinations lacks scientific validity or verification. There is no immunological requirement for annual vaccinations. The practice of annual vaccinations should be considered of questionable efficacy. Instead, clinicians, in the absence of legal requirements, should educate their clients that an annual physical examination is the better option.

Alternatives to vaccinations

Monitoring Serum Antibody Titers

As mentioned before, one of the "unknowns" with animal vaccinations is the duration of immunity. What this means is that the pharmaceutical companies have not determined how long a vaccination will protect against infection. One way to find out if an animal is still protected is to measure the amount or level of antibodies to a particular antigen is still present in the blood serum. This is called titering. Once an animal has been exposed to a particular disease pathogen the body makes antibodies against that organism. After they have done their "job", some of those antibodies change and become dormant so that the next time the animal is exposed to that same pathogen there is a stockpile of clones that can jump in and fight off that same infection. It is these antibodies that are being measured when an animal is titered. One point to consider is that titer levels do not really reflect the ability of an animal to fight of an infection, but rather how recently they have been "challenged" or exposed to that infectious agent. What this means is that the dog that stays at home and is never around other dogs is more at risk than those that have an active social life.

New Vaccination Protocols

Colorado State University
http://www.vth.colostate.edu/vth/savp2.html

UC Davis
http://www.vmth.ucdavis.edu/vmth/clientinfo/info/vaccinproto.html

University of Pennsylvania
http://www.vet.upenn.edu/comm/publications/bellwether/48/vaccination.html

University of Florida
http://www.vetmed.ufl.edu/sacs/Misc/2001vacprot.htm

Washington State University
http://www.vetmed.wsu.edu/rdvm/vaccine.html

Recent research may have uncovered the link between vaccinations and autoimmunity. Most autoimmune disorders appear to be triggered by some type of toxic assault or a viral or bacterial exposure. Why is this important? Preliminary studies have shown that something called molecular or antigenic mimicry may be involved. This intriguing model argues that the body is reacting to small protein-like fragments of the pathogen that are homologous to normal cellular components. If true, this would be a form of antigen or molecular mimicry in which antibodies formed against one molecule react with another similar looking molecule. Another factor to consider is illustrated in a recent study that showed that contaminants (specifically bovine thyroglobulin in rabies vaccine) that remain from growth of the cells in culture during vaccine production cause the dog to make antibodies against these contaminants. Since the bovine thyroglobulin molecule is very similar to the dog's own thyroglobulin, the antibodies produced against the bovine thyroglobulin cross-react with the dog's thyroglobulin. This could explain why so many dogs have thyroiditis characterized by high levels of antithryoglobulin antibody in their serum. This may in turn, explain why we currently have an epidemic of hypothyroidism in dogs in the United States.¹³

Vaccination Take Home Message

Vaccination should only be given at age appropriate times - the most common reason for vaccine failure is maternal antibody interactions.

1. Never vaccinate a dog that is ill or malnourished (the second most common reason for vaccine failure is nutritional deficits).
2. Only vaccinate for the: (a) "core" diseases like distemper and parvo, (b) those diseases appropriate for your dog's environment and (c) those mandated by law.
3. Follow the new guidelines for frequency of vaccinations and suggested combinations of vaccines.

Chapter 7
And What Of The Future...?

The fancy has traditionally selected dogs for breeding programs based on arbitrary conformation traits, rather than soundness of structure and overall health. In some cases, form no longer follows function. Breeders and clubs tend to focus on a handful of traits--if that many--at the expense of the whole dog. As for genetics, the relatively simple days of Mendel are not even a memory. Simple dominant or simple recessive genes do not cause most of the disease problems we face in purebred dogs--they are usually polygenic with most of the genes still unknown. What we should do revolves around the question of how to pick a potential breeder. DNA testing is expensive and, at this point in time, available for only certain diseases in certain breeds. The canine genome is not yet complete, and even when it is, it will be many years before the combination of genes causing diseases of interest are identified, and then years before tests are widely available for those diseases. These are noble and necessary goals for sure, but how do they factor into your life as a breeder? In truth, they don't. A word of caution is warranted here: do not hold your breath waiting for the magic test that will tell you whether or not to breed your dog. Let's look at practical and achievable solutions. There are two, and they have been right under our noses all the time: maintain genetic diversity and share information with each other. The goal of a breeder is to produce a "better"" dog. What constitutes improvement is at issue here. If you want to improve a breed, you must know the first principle of evolution. Evolution, by definition, is change and diversification over time in a species. However, if there is no genetic variability, there can be no evolution. Genetic variability is the result of naturally occurring mutations and recombination.

Maintaining Diversity

Maintaining genetic diversity will help control the expression of genetic disease, not eradicate it. We are talking quality of life for the individual dog. Genetic diseases do not skip from dog to dog as viruses do. You do not have to inoculate against genetic disease. All you have to do to keep genetically transmitted disease out of your line is not to breed affected dogs. Simply said but not easily achieved. Within this series of essays, we have explored the mechanisms underlying the disease processes, and yet, even with new and greater understanding, we have yet to find the solution to the problem. What it would take is a series of relatively minor but wide reaching changes in philosophy, policy and practice throughout dogdom--in essence, a paradigm shift.

First, clubs must talk to and educate their members, then achieve a cohesive consensus on breeding strategies that reduce the number of affected dogs. Second, clubs must talk to each other and form a coalition to fund studies that will lead to testing for genetic diseases. Third, the AKC must be convinced or otherwise encouraged to participate in a widespread reform and redefinition of breeding stock. Purebred registries should not be scrapped - there is too much history and tradition supported by a huge pyramid base of love and devotion to the dogs. What about adding new category: Breeding stock? Each parent club will have to define what is meant by "breeding stock" for their breed. The definition will involve a listing of the major genetic "faults" known in the breed. One could classify genetic faults by their severity:

Class I - Severe traits would include painful or disfiguring disorders that maim or otherwise cause the animal to be non-functional. Naturally, lethal traits or faults that require medical intervention or treatment for the duration of the animals life would be included in this category. Some few examples of this class: glaucoma, craniomandibular osteopathy, hip dysplasia, entropion, portal systemic shunts, cataracts, retinal dysplasia and detachment, PRA, deafness, dwarfism, inherited kidney disease, diabetes mellitus, hypothyroidism, epilepsy, copper toxicosis, ventricular septal defects, elbow dysplasia, and distichiasis.

Class II - This class would include genetic faults that are easily treated and respond well to therapy, those faults that are corrected by one-time surgery that could be considered primarily cosmetic, and those disorders that make the dog unsuitable for the purpose for which it was bred. Examples of this class would include bite misalignments, hernias, unilateral cryptorchidism, faulty dentition and gait abnormalities. Dogs accepted into the Breeding Stock Register of each club would have to be veterinarian-certified free of Class I or II faults.¹⁴

Examination and testing, consistent with current technology would be required as necessary to screen for the diseases recognized in the breed. A number of safeguards would have to be employed to ensure the purity of the Breeding Register. Absolute identification of the animal to include DNA identification, supported by a tattoo and/or microchip would be required. We are dealing with the breed's future, so no bogus registrations can be allowed. [Devil's Advocate time: What about late-onset problems for which there is no screening test? What about problems, like epilepsy, for which there is no positive testing process even for the afflicted?]

It is easier to get information from dissatisfied buyers about what they bought than it is to get information from breeders protecting their standing in the fancy. If breed clubs and AKC were to cooperate, any person registering a puppy, would receive along with the registration from the AKC, a postage-paid card to an open registry. If the puppy develops a genetically transmitted disease, this card would be completed by a veterinarian and forwarded to the registry.

Breeders might try to hide this information, much as they do radiographs of dysplastic dogs they do not send to OFA and PennHip. On the other hand, puppy buyers, who feel they spent good money for a product lacking in quality, would be more likely to comply. It would take only one of the puppy buyers from a litter with an affected puppy to file a report for the process to work.

The registries, if there were more than one cooperating with the AKC, would make their information easily accessible. They could be independent of the AKC or under contract or even be a division of the AKC. The important point is that the probability would be high that should a genetic problem show up in a litter, that litter and the pedigree supporting it would be flagged. Most puppies sold by breeders do not go to show homes and other breeders where this information could be carefully hidden. While the process might not be one hundred percent in 1 generation, over 5 or 10 generations, with a little computer-aided backtracking and cross-referencing, almost every litter with carriers or affected puppies could be identified. The nice thing about genetic disease is that if you know which litters had an affected puppy, you know which dogs to test. It is much easier and more economical to seek out, test and eliminate carriers if you know one of their littermates was affected.

The more conscientious and ethical breeders would also inform the puppy buyers and encourage them to report back any genetic faults encountered during the life of the puppy or in any of its get. As breeders, we leave a standing challenge to parent breed clubs, the AKC and the various registries to do something meaningful about the genetic problems plaguing the purebred fancy. We are not talking about lip service - we are talking about enlightenment, cooperation and action. Over the several decades that hip x-rays have been done, the incidence rate of hip dysplasia in the general dog population has been virtually unaffected. OFA and PennHip, both closed registries, have had minimal impact; and CERF probably less because most dog people do not have their dog's eyes examined every year. What we need are open registries with on-line searchable databases cross-referencing diseases to pedigrees.

One breeder at a time

It should be noted that people, even including scientists, are not always prone to rational facts. This especially applies to dog breeders. New and better information generally gets absorbed slowly. In the case of diversity, we need to struggle with long held beliefs that are no longer viable. Compounding the problem, in the case of inbreeding, these outmoded practices produce conformation ring success, but at what untold cost? Those of us who preach diversity find it very discouraging because these "old dogs" do not want to learn new tricks. If one hangs about the breed ring long enough, the prospect of educating breeders becomes overwhelming. However, instead of lamenting each incident and outcome of the old ingrained inbreeding paradigm we need to take one step at a time and rejoice in any and all progress. There is hope. It may be a human generation--and seven dog generation--away! But hope, nonetheless. You read this book, didn't you?

Appendix 1
Mapping out the dog's genetic future

Author's Note: This chapter is highly technical and will be of most interest to students of genetics.

In 1990, the greatest intellectual task ever attempted by humans began. Even more of a challenge than walking on the moon, the Human Genome Map Project staggers the imagination in terms of concept and complexity.

The ultimate intent of the project, completed in 2001, was to ascertain the definitive sequence of the more than 3 billion base-pairs comprising the human genome. A genome is all the genetic material in the chromosomes of a particular organism; its size generally is given as its total number of base pairs. This enormous effort has "spilled over" to other species, and dogs will reap the benefits. Building a road map of the dog's makeup through the Canine Genome Project eventually will lead to genetic tests that in turn may eradicate many genetic diseases. These results, which haven't the social, ethical and legal implications that muddy the waters of the human genome work, may be used to enhance the quality of our dogs' lives and help us back out of the genetic cul-de-sac in which we now find ourselves.

Pet owners spend billions of dollars every year diagnosing and treating genetic diseases afflicting their pets. We now have in our hands the elementary tools to prevent or ameliorate our dogs' physical suffering. Recently, in a truly international effort, the dog community took another small step forward: the publishing, far earlier than ever expected, of the first canine linkage map. Not only will this endeavor help to discover the basis for many genetic diseases in dogs, but the effort will spillover into human disease also.

The first of many hurdles

One of the biggest hurdles to overcome when mapping a genome, human or canine, is to assign a gene or genetic marker to a particular chromosome. Unfortunately assigning a genetic marker has been much more difficult because most of the canine chromosomes are the same shape and many are quite similar in size. Remember, besides the coding regions (i.e. genes), chromosomes include noncoding regions within the gene that act like spacers between the coding sequences. In addition, between the genes are long stretches of noncoding areas. It is in these sections that Mother Nature has given us a gift to help map the canine genome.

Interspersed along the entire length of the genome are regions called microsatellites. These areas of DNA consist of tandem repeats (identical or nearly so) of a short basic repeating unit, such as TGTGTGTGTGTGTG...ATTATTATTATTATT... etc. They can be mono-, di-, tri- or tetranucleotide blocks, and are referred to as short tandem repeat polymorphic (STRP) markers. Considered in evolutionary terms, these regions tend to show a higher percentage of variations, therefore even closely related individuals will exhibit differences. These variations can be as simple as a change of one base-pair, called a point mutation, or as different as the deletion or addition of base-pairs. For example, these repeats usually appear in blocks that vary from 10 to 30 units long. A puppy could inherit a (TG)₁₀ from its dam and a (TG)₁₄ from its sire. If the pup carries enough of these parental type alleles, it is possible to ascertain parentage. However, further variations in additional markers would be necessary to differentiate between siblings.

Identifying genetic markers

It has been suggested that it will require several thousand microsatellites to saturate the canine genome. This means that there will be a marker about every 3 megabases (a megabase is 1 million base-pairs). This will ensure that once these markers have been identified, at least one of them will be associated with, and inherited along with, a specific gene. Once a marker has become linked to a particular gene that has been characterized for a specific trait or disease, it then can be used as a diagnostic tool to screen for a desired characteristic. It would also be useful in identifying a carrier (or an affected individual) of a genetically transmitted disease. This would be extremely valuable information, as many inherited diseases are of the late onset type, meaning the disease does not become evident until the dog is well past the age where it might have been used for breeding.

Nature's scissors

Another handy tool for the geneticist was discovered some 30 years ago. Scientists were able to isolate several proteins from various strains of bacteria, named restriction enzymes because they cut DNA at specific sites. The normal function of these enzymes was to protect the bacteria from attack by phage (viruses that infect bacteria) or other foreign DNA. Each restriction enzyme recognizes a particular double-stranded DNA sequence. This specificity has been extremely useful for mapping the genome. Hundreds of restriction enzymes have been isolated. Depending upon the source, these enzymes "see" restriction sites that vary from four to eight base-pair recognition sites.

Some rare-cutter enzymes cut DNA very infrequently, which results in a small number of very big pieces. The use of simple sequence repeats in identifying canine polymorphic markers has been a fairly recent innovation. Prior to this, a technique called restriction fragment length polymorphism (RFLP) markers were used to construct gene maps. Using restriction enzymes that recognize base-pair sequences, it is possible to cut DNA into various lengths. These segments can be separated by gel electrophoresis. DNA carries an overall negative electric molecular charge. Under the influence of an electric field, the different fragments migrate toward a positive charge at a speed that corresponds to their molecular weight. Since the shorter fragments travel faster than the longer pieces, it is possible by using this technique to differentiate between segments that differ by as little as one nucleotide.

RFLP thus provides the basis for a technique called DNA fingerprinting that can establish a parent-progeny relationship. The chief disadvantage of this procedure is that it is extremely labor intensive (read: expensive) and requires a great deal of genetic material. Tandem repeat markers have an advantage over RFLP because they can be assayed by polymerase chain reaction (PCR) and have a higher polymorphic information content (PIC). For this reason they have become the basis of the DNA parentage verification tests in use today.

PCR is a technique that increases a specific section of DNA about 1 million times. Since it is an automated procedure, the reaction can be repeated as many times as needed to obtain ample DNA for that area being investigated. The DNA is then separated using gel electrophoresis, and because the variations in length correspond to those of the repeat sequence, it is possible to recognize individual differences. The main drawback of this procedure is that the primers used in PCR amplification for a dog are not always the same for other mammals, so unique markers must be developed for every species.

The term PIC is a little more complex. If a marker is to be useful, it must be unique. As the number of variations within each marker increases, it becomes more and more individualized and therefore has a higher polymorphic information content. This is a little like saying my house is on First Street, then adding that it is on the corner of First Street and B Avenue. If next I say it is on the northwest corner, it is easier to locate. Then if I add that it is a white house with green shutters, etc., you can see that each little bit of information increases the ability to find my house. It is these characteristics that make markers useful for parentage verification and for the purposes of positive identification of the animal. Remember it is possible to see chromosomes only in certain phases of the cell cycle. The best time to see them is during metaphase. Normally, chromosomes exist in a dispersed state that cannot be seen with an ordinary light microscope. Just before the cell divides, it tightly gathers up its chromosomes. While in this state of metaphase, it is possible to take a picture of all the chromosomes in the cell. As you recall this picture is referred to as the karyotype, and in this picture, we can see the number of chromosomes, their size and their physical appearance.

Standardization of the canine karyotype was necessary before researchers could relate genes or genetic markers to their chromosomal origins. Development of chromosome-specific markers will ensure that all of the canine chromosomes will be represented within the map and that the linkage groups are correctly orientated. This difficult barrier has been overcome by some brilliant work in England. Knowing the dog has 39 haploid chromosomes (half of 78 is 39), researchers used a male dog in their experiment because it is easy to see the Y chromosome. That left 38 chromosomes to identify.

The researchers first separated the chromosomes by their DNA content and the use of two fluorescent dyes that distinguish the base-pair ratio by preferentially staining either A-G or C-T rich regions. Using a technique called dual-laser flow cytometry, they were able to resolve their sample into 32 different components. Twenty-two of the portions contained single chromosomes, and the remaining eight had two each. Thus, all of the chromosomes were accounted for.

To identify the chromosome type, they then used these fractions to "paint" a normal metaphase chromosome spread (a cell that has been "fixed" chemically so it no longer cycles) and highlight the chromosomes using another technique called FISH (fluorescent in-situ hybridization).

Hybridization is a very important concept to understand because it is the basis for many of the methods used to study DNA. Recalling that the two possible DNA base-pairs are C-G and A-T, if you have a DNA strand that reads AATGGCTAT, its complimentary strand would have a base-pair sequence of TTACCGATA. In FISH, complementary strands of DNA or RNA preferentially bind to each other. If one of the strands is tagged with a fluorescent dye, it can be used to locate its equivalent complement on another DNA strand. Other types of probes use radiographic or immunological labels. Hybrid probes will be addressed in detail when we discuss mapping strategies.

Mapping our way

Just like maps we use to find our way around town, genetic maps establish spatial organization and symbolize a wide variety of information. They also are similar in that there are different types of genetic maps, each with a corresponding range and level of precision.

The karyotype (also known as a cytogenic map) is the lowest resolution of what is known as the physical map. The highest resolution would be to know any posttranscriptional modifications (changes in the RNA after DNA transcription) once we know the entire base-pair sequence. Another type of genome map is a linkage map. The final genetic map will be a synthesis of physical and linkage maps. This new map will let us know which chromosome a gene is on, how many base-pairs separate each genetic marker, their positions relative to each other and ultimately the complete basepair sequence. Once the entire sequence has been resolved, we will need to find all the genes and use this information to determine their function. The medical applications of this map alone are overwhelming. These data, used as diagnostic tools to identify deleterious mutations, combined with future gene therapy technologies, could lead to the eventual eradication of genetic disease. We also could learn how certain behavioral traits are transmitted, which is of especial interest to dog breeders.

Making the linkage

In 1865, the father of modern genetics, a young monk named Gregor Mendel, published a paper in which he described the inheritance of certain traits he had observed while growing peas. In choosing which attributes to follow, Mendel was very lucky that he chose the characteristics he did, as they all turned out to be on different linkage groups. As a rule, we equate linkage groups with individual chromosomes, and the number of linkage groups corresponds to the haploid number of chromosomes. Thus, the dog has 39 linkage groups.

Mendel's observations led him to postulate two "laws". The first law says "particular factors" (genes) come in different forms (alleles). When gametes are formed, these alternative alleles are inherited independently from each other. Mendel's second law predicts that different genes (i.e., different traits that are not on the same chromosome) will assort themselves into two different types of progeny in statistically equal amounts. These two types are the parental type and the recombinant type. However, when the genes that code for those traits are on the same chromosome, the percentage of recombinant types would be less than the anticipated 50 percent. American geneticist Thomas Hunt Morgan suggested this lowered recombination rate simply was a function of how far apart the genes were from each other. The closer together they were, the more likely they would stay 'linked.' We can use this information to predict the relative distance between the loci of two genes. Today we measure the distance that separates genetic markers in centimorgans (cM). Two loci are said to be 1 cM apart if they are separated by a recombination event one percent of the time. This roughly corresponds to a physical distance of one million base-pairs.

The next step in the mapping process is to determine the linear order of the genetic markers. For instance, let's say Gene A is 5 cM from Gene B and Gene B is 7 Cm from Gene C. If we then find out Gene A is 12 cM from Gene C, we can assume their relative positions are Gene A.....Gene B.......Gene C.

It would be nice if it were this easy. Unfortunately it is not. Coding regions, also know as exons, are just too far apart to be linked conveniently, and so we need to use other types of genetic markers. Another problem is that, compared with bacteria or fruit flies, the dog has too few progeny to generate the statistical recombination data needed. Humans have even fewer offspring.

The discovery and use of microsatellites, the genetic markers in the noncoding introns of the gene, has overcome this barrier. So far, about 1800 canine microsatellites have been characterized. At this time, markers have been found for 98% of the canine genome.¹⁵ In order to be useful, these markers must be similar within species, breed and family groups, yet be different enough (polymorphic) to detect the differences among individuals.

To repeat, microsatellites exist as di-, tri- and tetra repeat patterns, but because of founder effect and the tight "linebreeding" inherent in the purebred dog, the most useful microsatellites for elucidating the canine linkage map have been tetra repeats. Although these areas are not genes, differences in the number of copies of the basic repeat unit also are called alleles (length polymorphism). Because of technological advances, it is fairly easy to ascertain the difference between two genotypes, and these procedures are the basis for the most commonly used parentage tests now available. The more alleles a microsatellite has, the more likely it is to be useful.

Mutations that occur within these regions do not cause changes in the dog's appearance, behavior or health; however, linking these genetic markers to disease alleles or genes that characterize a specific trait will lead to diagnostic tests to identify carriers or affected individuals. Several of these tests already are available. These microsatellites are especially useful for identifying the carrier status of genetic disorders that arise from mutations at different sites within the same gene. This is why breed-specific tests often are required for the same disease.

Recombinant DNA technology promises to make higher resolution linkage maps possible. A lab in France has used radiation to fragment human chromosomes and has fused these fragments with cells from other species. These hybrid cells can be manipulated so that only specific human chromosomal components are retained. Determining the frequency of genetic markers that stay together after being irradiated places their order and the distance between them at a finer resolution. These techniques also have overlapped into the canine mapping effort. Work is progressing rapidly on a radiation hybrid panel specific to the dog.

The physical mapping realm

In addition to the linkage maps, there are several types of physical maps:

Chromosomal maps

Keep in mind that the lowest-resolution physical map is called a cytogenetic map (karyotype). During the metaphase and the interphase stage of the cell cycle, it is possible to stain the chromosomes with various dyes that result in distinctive banding patterns. Using radioactive or fluorescent labels it is possible to assign genes or other identifiable DNA fragments to their respective chromosomes and to estimate the distance between them, measured in base-pairs. Improved FISH methodology now allows identification of genetic markers from as close as 2Mb to 5 Mb apart (one Megabase, or Mb, equals approximately 1 cM). With FISH, we can observe chromosomal mutations and abnormalities associated with disease states. German researchers have discovered a translocation on the first canine chromosome (a type of mutation - see Ch. 2) that is linked to mammary tumors in dogs. Cytogenetic analysis may prove useful for comprehending the underlying genetic mechanisms for other types of cancers for dogs and humans.

Complementary DNA (cDNA) maps

Although two genetic markers may have a recombination rate higher than 50 percent, this does not preclude them from being on the same chromosome. This further complicates the mapping issue. The trick is finding out which of the 39 unique dog chromosomes to assign a particular gene to. One of the methods used depends on knowing the protein the gene is responsible for making, then working backward to figure out the approximate DNA sequence. Using a tagged complementary hybrid probe made from a synthetic DNA sequence, it is possible to see where the gene is located on the chromosome.

Another way to map a gene to a chromosome is to know the base-pair sequence of the gene that codes for the same trait in a related species. For example, all mammals have some genes in common. We even share conserved sequences - base sequences in a DNA molecule that have remained essentially unchanged through evolution - with the lower orders of animals. Although entire chromosomes are not conserved among species, parts of chromosomes, called syntenic groups, are.

Homologous genes and genetic markers from the human mapping project have been beneficial to the canine map effort. In turn, the canine map has been expected to be useful to the Human Genome Project. Knowing the function or position of a certain gene in one species makes it a possible candidate gene for the same ailment or trait in another species. One such ailment, Severe Combined Immunodeficiency (SCID), is caused in humans and canines by a mutation in one of the proteins that form the receptor site for interleukin-2. Interleukin-2 is a chemical messenger that improves the bodies response to disease. This specific defect causes a profound inability to mount both a cell-mediated and humoral (antibody) immune response. It frequently is called the "Boy in the Bubble" disease because of the movie about a boy with this affliction who lived in an isolation bubble.

Several different laboratory techniques are used to localize differences to a smaller region of the genome. Once such an area has been identified, it is possible to use automated sequencing methods to distinguish any base-pair mutations. If these mutations result in an amino acid substitution within the coded protein product, it becomes a likely suspect. The candidate gene approach can save a lot of time, not only by providing a model for the progression and course of a disease, but by suggesting treatment strategies.

Contig maps:

A better technique for obtaining finer mapping details is the contig map, produced by cutting a chromosome into very small pieces, cloning these pieces and constructing an overlapping clone "library."

This kind of cloning is a recombinant technique that involves inserting a DNA segment into another host cell, called a cloning vector, and using that cell's own replication apparatus to generate multiple copies of foreign DNA. This provides large amounts of experimental material.

Cloning vectors often are bacteria such as E.coli, but recent technological advances have made it possible to clone larger segments of DNA by using an artificial cloning vector packed into a lamda phage. This virus normally infects bacteria and inserts its own DNA into that cell's genome, where it is replicated along with the normal cellular DNA. Using nature's own tricks has often worked well for us in this endeavor. Once contig mapping of a particular section of the genome is accomplished in one laboratory, the resulting genetic library can be published so other researchers can use the same information. A common reference system called sequence-tagged sites makes this sharing of information possible. STS are short DNA fragments (200 to 500 base-pairs long) whose unique base sequence and location make them useful landmarks. A variation of this method is to sequence cDNA partially instead of random sections of DNA. Complimentary DNA is a special type DNA that is synthesized from a messenger RNA template. This is reverse of the process as it normally happens. Since they are "tagging" a transcription product of an expressed gene, they are called expressed sequence tags, or EST. These are especially useful for finding candidate genes.

We have only just begun

Current mapping strategies, as brilliant and innovative as these techniques are, still have left gaping holes that need to be filled. Genetic mapping is technology-driven, but technology costs money and time. Faster, more precise mapping methods are needed. Funding for the canine project generally takes a back seat to funding for the human mapping effort and for species that are more agriculturally and economically important than the dog. But it must be done as this information will provide us with the basis of all genetic testing and strategies for coping with genetic disease.

Where is the money to come from? It is most likely that if genetic testing is embraced by the dog fancy, market pressures will result in development of new tests, some of the profits from which will be used to fund further research. If breeders do not test for genetic disease, who will?

For breeds at great risk, certain breeding strategies such as introgression, a very complex method that involves going back to the original stock and selecting for or against a particular gene trait, should be considered. We need to contemplate opening up the studbooks. At present, studbooks are closed. The only way to get back some of our lost genetic diversity is to breed those dogs that made up the breed originally. The AKC could have a set procedure for going back to the original foundation stock, even when there is no actual breed registry in the original country. As it now stands, each breed club is being asked to "reinvent the wheel" in this endeavor. The Samoyed, Saluki and the Basenji are perfect examples of this predicament because seldom have tribal peoples from whence these dogs came, maintained written records. Some hard questions also need to be asked about the validity of our pedigrees and what must be done to protect those records. The fancy must address these problems if our beloved animals are to have a viable future. We are the custodians of our various breeds, thus the responsibility for finding answers to these genetic problems is ours.

Appendix 2
Glossary

Acrocentric - A chromosome with the centromere located close to one end.

Allele - Alternative forms of a genetic locus; a single allele for each locus is inherited separately from each parent, each locus may have multiple alleles possible however only two are available at a time, one from each parent.

Apoptosis - Natural process of cell death.

Assortative Mating - The mating of individuals that are phenotypically similar. Assortative mating means mating like with like.

Autosomes - A chromosome not involved in sex determination.

Autosomal chromosomes - see Autosomes

Base pair (bp) - Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs.

Candidate gene - a gene which researchers feel is likely to be one which performs a particular function because it performs a similar function in another species. Further research will be required to determine if it is or is not the gene being sought.

Centriole - A structure that appears in pairs within the cell during the interphase portion of cell division. During prophase the two asters migrate to opposite poles of the cell and begin organizing spindle fibers which will guide the duplicated chromosomes toward the asters prior to completion of cell division.

Centromere - A structure which joins two paired chromosomes together.

Chromatin - The tangled fibrous complex of DNA and protein within a eukaryotic nucleus. See: chromosome.

Chromosomes - The self-replicating genetic structures of cells containing the cellular DNA that bears in its nucleotide sequence the linear array of genes.

Co-dominant - Alleles of a gene which will both express in a heterozygous individual. ExHumanB blood type.

Codon - The basic unit of the genetic code, comprising three-nucleotide sequences of messenger ribonucleic acid (mRNA), each of which is translated into one amino acid in protein synthesis.

Complete (simple) dominant - An allele which will be expressed in the phenotype even if in a heterozygous pairing with another allele.

Constitutive heterochromatin - Condensed segments of the chromosome which are transcriptionally inactive in all cells.

Contig map - A chromosome map that is formed by rendering chromosomes into small pieces, cloning them then forming a "library" of overlapping cloned segments.

Cross Breeding - The mating of two recognized breeds to establish a new variety or to improve an existing one.

Crossing over - See "recombination".

Cytogeneticist - A scientist who studies cellular genetics.

Cytoplasm - The protoplasm of a cell exclusive of that of the nucleus, it consists of a continuous aqueous solution (cytosol) and the organelles and inclusions suspended in it and is the site of most of the chemical activities of the cell.

DNA (deoxyribonucleic acid) - The molecule that encodes genetic information. DNA is a double-stranded molecule held together by weak bonds between base pairs of nucleotides. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus the base sequence of each single strand can be deduced from that of its partner.

Degeneracy - Term used to note that more than one codon can represent an amino acid.

Differentiation - Process of cellular development into different types of tissue.

Diploid - A full set of genetic material, consisting of paired chromsomes one chromosome from each parental set. Most animal cells except the gametes have a diploid set of chromosomes. See haploid

Disassortative Mating - The opposite of assortative mating, i.e., the mating of dissimilar phenotypes.

Dominant - A gene is said to be dominant if it expresses its phenotype even in the presence of a recessive gene.

Epistasis - A process by which the expression of one gene will prevent the expression or influence the expression of another.

Exons - The protein-coding DNA sequences of a gene. See intron.

Euchromatin - Portion of the chromosome that is transcriptionally active.

Expression - The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into a protein like mRNA.

Facultive heterochromatin - Bunched segments of the chromosome that are transcriptinally inactive and which vary by cell type.

Founder effect - Changes in allele frequencies that occur when a sub-population if formed from a larger one. Founders of the sub-population may have among them greater or lesser percentages of particular alleles than is the case for the population as a whole.

Free radical - Highly reactive oxygen molecules that occur naturally in the body because of metabolic processes which can damage DNA.

Gamete - Mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes.

Gene - The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule). See expression.

Gene frequency - Percentages of the different alleles of a particular gene that are found in a population. Also referred to as "allele frequency."

Genetic diversity - Percentage of genes that are polymorphic in a population; sometimes refers to the proportion of genes that are heterozygous.

Genetic drift - Changes in gene frequency due to random chance (as opposed to selection or mutation.)

Genome - The complete nuclear DNA sequence of a species, including all variations.

Genotype - The genetic constitution of an organism. See phenotype.

Haploid - A single set of chromosomes (half the full set of genetic material), present in the egg and sperm cells of animals.

Haplotype - Set of linked genes on a single chromosome, usually inherited as a unit.

Heritability - Portion of phenotypic variation possible due to genetic inheritance as opposed to environmental influence.

Heterochromatin - Bunched segments of a chromosome which are transcriptinally inactive.

Heterozygous - Containing two different alleles of the same gene. See homozygous.

Homologous pairs - A pair of chromosomes containing the same linear gene sequences, each derived from one parent.

Homozygous - Containing two copies of the same allele. See heterozygous

Hybridization - The crossing of two distinct strains, sometimes across species lines (i.e. a mule.)

Imprinting - The expression of a gene determined by which parent it has been inherited from.

Inbreeding - The mating of related individuals; also includes what dog breeders term "linebreeding." The technical definition is the breeding of animals which results in progeny having a greater coefficient of inbreeding than is the average for the breeding population.

Incomplete dominance - Alleles that, when heterozygous, result in a phenotype intermediate between those of the homozygotes of those alleles.

Interlocus - Reaction between genes, as in epistasis.

Intralocus - Reaction between alleles of a particular gene.

Introgression - The expansion of the gene pool of a population via the introduction of unrelated individuals from another population (i.e. through imports or cross-breeding.)

Introns - The DNA base sequences interrupting the protein- coding sequences of a gene; these sequences are transcribed into RNA but are cut out of the message before it is translated into protein. See exons.

Kinase - A type of enzyme that that catalyzes the conversion of proenzymes to active enzymes.

Karyotype - An individual's chromosome complement; also the arrangement of chromosomes at metaphase into a sequence ordered by length and location of the centromere.

Lamda phage - A bacterial virus used as a cloning vector.

Line breeding - The mating of later generations back to some ancestor or its descendents. Line breeding is a form of inbreeding.

Linkage - A measure of the frequency at which two genes on the same chromosome will pass together to gametes.

Linkage disequilibrium - The tendency of alleles of closely linked genes to be inherited together.

Locus (pl. loci) - The position on a chromosome of a gene or other chromosome marker; also, the DNA at that position. The use of locus is sometimes restricted to mean regions of DNA that are expressed.

Major Histocompatability Complex (MHC) - A group of genes that govern immune system function, all closely linked on a single chromosome.

Meiosis - The process by which germ-line cells produce gametes.

Messenger RNA (mRNA) - RNA that serves as a template for protein synthesis.

Metacentric - Chromosomes in which the centromeres are located mid-way down their length.

Methylation - The addition of the functional group - CH3. This plays a role in gene expression and in post-transcriptional modification.

Microsatellite - Highly repetitive segments of non-coding DNA, often used for parentage verification or as markers in indirect gene tests.

Mitosis - The process by which cells divide.

Monosomy - Occurs when an individual has inherited only one copy of a chromosome; in mammals this is lethal not long after fertilization.

Mosaicism - The phenotypic effect of the random deactivation of one copy of the X chromosome.

Mutation - A permanent transmissible change in the genetic material, usually in a single gene. Also, an individual exhibiting such a change.

Natural selection - Process that results in adaptation of an organism to its environment by means of selectively reproducing changes in its genotype. Variations that increase an organism's chances of survival and procreation are preserved and multiplied from generation to generation at the expense of less advantageous variations. As proposed by Charles Darwin, natural selection is the mechanism by which evolution occurs. It may arise from differences in survival, fertility, rate of development, mating success, or any other aspect of the life cycle. Mutation, gene flow, and genetic drift, all of which are random processes, also alter gene abundance. Natural selection moderates the effects of these processes because it multiplies the incidence of beneficial mutations over generations and eliminates harmful ones, since the organisms that carry them leave few or no descendants.

Neotany - The tendency of a species to retain infantile or juvenile characteristics.

Nondisjunction - An error of cell division that allows two copies of a chromosome to wind up in a single daughter cell or gamete, ultimately causing trisomy or monosomy.

Nucleic Acid - Linear polymers of nucleotides. Nucleotides form the basic building blocks of nucleic acids. They are made up of a nitrogen-containing purine or pyrimidine base linked to a sugar (ribose or deoxyribose) and a phosphate group.

Nucleotide - A subunit of DNA or RNA consisting of a nitrogenous base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). Thousands of nucleotides are linked to form a DNA or RNA molecule.

Nucleus - The major organelle of eukaryotic cells, where the chromosomes are separated from the rest of the cell by the nuclear envelope

Outbreeding - A term generally taken to be the opposite of inbreeding. It can be applied to outcrossing or cross breeding.

Outcrossing - Breeding from totally unrelated animals of which one is or both are inbred (or linebred) within a given breed.

p - The short arm of a chromosome.

Penetrance - The frequency with which a genotype will produce a phenotype.

Phage - Viruses which infect bacteria.

Phenocopy - Different genes which produce similar phenotypes.

Phenotype - The physical appearance/observable characteristics of an organism. See genotype.

Pleiotropic - The ability of a single mutation affect several traits.

Polygenetic - A trait resulting from the action of multiple genes.

Polymorphic - A gene which has multiple alleles. It also applies to non-coding regions.

Polypeptide - A peptide containing more than two amino acids and that are named according to the number of amino acids they contain.

Posttranscriptional modifications - Changes in the RNA after DNA transcription.

Primary transcript - RNA transcript immediately after transcription in the nucleus, before RNA splicing to form the mature mRNA.

Promoter - Regulatory section of DNA to which RNA polymerase binds prior to transcription.

Protein - A large molecule composed of one or more chains of amino acids in a specific order; the order is determined by the base sequence of nucleotides in the gene coding for the protein. Proteins are required for the structure, function, and regulation of the bodys cells, tissues, and organs, and each protein has unique functions. Examples are hormones, enzymes, and antibodies.

q - the long arm of a chromosome.

Reading frame - A contiguous, non-overlapping set of triplet codoms in RNA or DNA that begin from a specific nucleotide.

Recombination (homologous) - The exchange of DNA fragments between two DNA molecules or chromatids of paired chromosomes (during crossing over) at the site of identical nucleotide sequences.

Recessive - A gene that is expressed only when it is present in two copies or if the other copy is missing. See dominant.

Recombination - Process by which like segments of homologous chromosomes will exchange places during meiosis.

Regulatory gene - One that is involved in the control of other genes.

Retroviruses - Any virus in the family Retroviridae that has RNA as its nucleic acid and uses the enzyme reverse transcriptase to copy its genome into the DNA of the host cells chromosomes. Many cancers in vertebrates are caused by retroviruses.

RNA (ribonucleic acid) - A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose.

RNA polymerase - RNA enzyme involved in the transcription of DNA.

Sex linkage - Inheritance patterns resulting from genes located on the sex chromosomes.

Simple dominance - See "complete dominance".

Structural gene - One that encodes amino acids that ultimately lead to formation of tissues or the regulation of body functions.

Submetacentric - Chromosome in which one arm is slightly longer than the other.

Suboptimal - An allele that causes slightly reduced function.

Syntenic groups - Genes on the same chromosome.

Template - Section of the DNA that is copied by RNA.

Transcribed (transcription) - The synthesis of a RNA copy from a sequence of DNA (a gene); the first step in gene expression. See translation.

Translation - The process in which the genetic code carried by messenger RNA directs the synthesis of proteins from amino acids. See transcription.

Triploidy - A condition in which a cell or individual has three copies of a chromosome.

Trisomy - Occurs when an individual has inherited three copies of a chromosome; in mammals this is lethal before or shortly after birth.

Uniparental disomy - condition in which an individual inherits two copies of a chromosome from one parent and none from the other.

The Y chromosome - the small chromosome that is male-determining in most mammal species. The male has one Y chromosome and one X chromosome. The Male Specific region (MSY) comprises 95% of the chromosomes length and is made up of heterochromatic areas (condensed during the interphase portion of the cell cycle) and three 3 specific euchromatic (diffuse during the interphase portion of the cell cycle) areas. So far only the euchromic areas have been found to contain transcription factors, including coding genes. One region of the euchromic region is homologous to and pairs with the X chromosome and is now called the x-transposed region. It contains 2 coding genes that are expressed in the testis. The x-degenerate region is composed of ancient remnants of autosomes (non-sex determining chromosomes) from which both the x & y chromosomes evolved. It contains 16 coding genes that are expressed widely in all the tissues of the body. (These genes have x-linked homologues) The amplionic region contains 60 coding genes that are linked to male sexual development with regard to sperm development and triggering appropriate hormonal output.

Appendix 3

"The Additive Relationship is the most commonly used measure of relationship. It is a measure of the fraction of genes shared by two animals and thus is an indication of how reliable one of the relative's records will be in predicting the genetic value of the other animal. The Inbreeding Coefficient of an animal is calculated as one-half the Additive Relationship between the parents." (p199, "Genetics for the Animal Sciences," LD Van Vleck, EJ Polak, EAB Altenacu, 1987)

Additive Relationship is twice the Coancestry (which is also called the coefficient of kinship or of consanguinity), "The coancestry of any two individuals is identical with the inbreeding coefficient of their progeny if they were mated. Thus the coancestry of two individuals is the probability that two gametes taken at random, one from each, carry alleles that are identical by descent." (p85, "Intro. to Quantitative Genetics," Falconer & Mackay, 4th Ed., 1996)

The important difference between the COI and the coancestry (one-half the additive relationship) is that one, the COI, refers to the individual animal. The coancestry refers to the genetic similarity between two animals.

A bitch "Jacki" might have a high COI. A dog "Jessie" might have a high COI. But the coancestry of Jacki and Jessie might still be low or even zero. If this is the case, then both Jacki and Jessie are inbred (in fact, the entire breed line might be inbred), but there is still significant genetic diversity in the breed line if Jacki and Jessie have a low coancestry.

Continuing - If Jacki and Jessie have high COIs, they are prone to all the problems associated with inbreeding. If the average COI for the breed line is high, then the whole breed line is inbred and is likely to suffer the consequences as reflected in rates of hereditary defectives, increased puppy mortality, and reduced longevity. Yet, a low average coancestry for the breed line implies that there is a lot of latent genetic diversity in that same breed line. If so, the breed line can be salvaged by the appropriate choice of mates.

So when you discuss the genetic health of a single animal, consider its COI. When you discuss the latent genetic health of a breed (or a breed line), consider the average coancestry. To compare coancestry figures be certain that they are computed to the same depths of pedigrees (same as with COI comparisons).

 

Canine Hip Dysplasia, Part II

By Susan Thorpe-Vargas Ph.D., John Cargill MA, MBA, MS.
(Reprinted with permission).

Causative Factors of Canine Hip Dysplasia

Owners must separate fact from myth when examining theories on genetic, nutritional and environmental factors that influence CHD.

This is the second part in a series on canine hip dysplasia. What follows is written from the perspective that the readers of the series are conscientious breeders who are the guardians of the genetic pools that constitute their breeds. While this series of articles will not replace a stack of veterinary medical texts, it is a relatively in-depth look at the whole problem of a canine hip dysplasia. Furthermore, the series is designed to be retained as a reference. When you finish reading it you will have a sufficient background to make rational breeding choices and will be able to discuss the subject from an informed basis with your veterinarian. You may not like what you read, but you will be more competent to deal with the problem.

Conclusions from Part I: Genetics is the foremost causative factor of canine hip dysplasia. Without the genes necessary to transmit this degenerative disease, there is no disease. Hip dysplasia is not something a dog gets; it either is dysplastic or it is not. An affected animal can exhibit a wide range of phenotypes, all the way from normal to severely dysplastic and functionally crippled. Hip dysplasia is genetically inherited.

In this article we will address the issue of genetic, nutritional and environmental factors. We hope to debunk some of the myths and introduce some recently developed theories.

Other diseases, infections or trauma can produce clinical signs suggestive of canine hip dysplasia. In some breeds the animals learn to live with pain and are stoic about letting anyone know of their pain. This stoicism seems to be especially prevalent in terriers and northern breeds and is the case - not the exception - in the fighting breeds. Those fanciers who participate in pulling, freighting, carting or sledding events with their dogs should always be aware that tendonitis or pulled muscles can cause a gait change reminiscent of hip dysplasia. Anyone involved in lure chasing or coursing for real needs to understand that on occasion, an animal will twist or turn the wrong way while in full chase. In the older dog, trauma from younger years may manifest itself as arthritic deterioration. A little bit more unusual is to have viral penetration of the joint capsule with resultant damage to articular cartilage, or the epiphyseal surfaces of the femur. Absent such unusual occurrences, the reality of hip dysplasia is that it is a genetically linked condition--always was, always will be.

The role of growth

In the first article we said that the first six months of a puppy's life seem to be a critical time of development. The rate of growth can be astonishing. When one thinks of the number of things that could go wrong as an Akita puppy, for instance, goes from a birth weight of slightly more than 1 pound to 60 to 70 pounds in six months and then adds another 30 to 40 pounds by year end, it is amazing that most dogs mature without serious problems. It is during this period that dogs are most active. There is evidence to suggest that exercise is necessary to retain the depth of the acetabulum. How much exercise and of what type is unknown.

One Norwegian anecdotal study published in England in 1991 concluded that German Wirehaired Pointer, English Setter, Irish Setter, Gordon Setter and Labrador Retriever puppies growing up during the spring and summer had a lower incidence rate of hip dysplasia than puppies growing up during autumn and winter. Oddly enough, Golden Retrievers and German Shepherd Dogs did not manifest the same seasonal pattern of incidence of hip dysplasia. ^[1]

While this study may lack strict experimental protocol, it raises many questions. The first question is whether there was an exercise differential between the dogs due to weather in Norway. The second question was whether there was different availability of sunlight necessary for vitamin D production and utilization. The list of questions could go on, but this study is brought up to show that there may be exercise and diet factors at play, and that various breeds may respond to these factors in different ways. It would be reasonable to conclude that there is probably an amount of exercise during a genotypically dysplastic puppy's rapid growth period where phenotypic expression is mitigated, delayed, or both. Without taking the time, cost and effort to conduct a rigorous scientific study, it is still sometimes possible to glean valuable information from existing, i.e., available data. Therefore, do not shy away from creating working hypotheses from anecdotal studies; conversely, do not lock their findings in concrete as inviolate fact.

With respect to the published scientific literature, we found nothing in Medline (an online listing of medical and biological articles) referencing any journal article addressing the subject of surfaces and their effects on the incidence of hip dysplasia. While we know of breeders who write into their sales contracts that animals must be kept on a specific surface and fed a specific feed, these demands seem to be without scientific basis.

There is some evidence that preventing rapid growth reduces the extent to which the adult dog will manifest hip dysplasia. Decreasing the dog's food consumption during its growth period seems to correlate well with normal hips. ^[2] The Kealy study published in 1992 was based upon 48 8-week-old Labrador Retriever puppies. These puppies were sex-matched littermates randomly assigned to two groups: the first group was fed ad libitum (as much as they wanted, when they wanted to eat); the second group was fed the same feed until they were 2 years old, but in amounts of only 75 percent of what the first group consumed ad libitum. Thus for every puppy fed ad libitum, there was a same-sex littermate on a restricted diet. This rigid protocol gives this study great respectability and credence. The accompanying chart gives the findings in tabular form. Note the tremendous increase in normal animals at two years of age when kept on a restricted diet for those two years. This ought to more than suggest that overweight animals are at risk for phenotypic expression of canine hip dysplasia.

Radiographic Evaluation Method	Group 1 Ad Libitum Feeding			Group 2 75% of Ad Libitum Feeding
	Dysplasic	Normal	% Normal	Dysplasic	Normal	% Normal
OFA Swedish	16 18	8 6	33% 25%	7 5	17 19	71% 79%

Many researchers conclude that early fusion may lead to bone and cartilage deviations which then could predispose the animal to future dysplasia. An important point that these studies illustrate is that it is possible to improve the individual phenotype of dogs whose parents carried the gene for hip dysplasia (genotypically dysplastic).

In the first article we alluded to joint laxity as being present whenever there is canine hip dysplasia. Given that joint laxity is at least one of the factors governing the onset of hip dysplasia, then any process that retards this condition could possibly minimize the severity of the disease. It also is conceivable that retardation of joint laxity could delay the onset of the physical appearance of the disease.

Feed for health

A recent study (1993) showed that coxofemoral joint stability was improved in dogs that were fed increased levels of chloride and decreased levels of sodium and potassium. ^[3] In the eight-part "Feed That Dog!" series (Dog World, July 1993 through February 1994) we emphasized repeatedly the importance of the ratio of sodium and chlorine, with a ratio of 1.5 sodium to chlorine being accepted as the dietary requirement. ^[4] We noted also that "sodium chloride deficiency is manifested by fatigue, decreased utilization of protein, decreased water intake, inability to maintain water balance, retarded growth, dryness of skin and loss of hair." ^[5] Potassium deficiency " results in poor growth, restlessness, muscular paralysis, a tendency toward dehydration, and lesions of the heart and kidney." ^[6] We cautioned that "prednisone, a steroid commonly prescribed for various skin allergies, causes a loss of potassium and retention of sodium, and retention of sodium can cause further loss of potassium." ^[7]

Calcium (Ca), sodium (Na), and potassium (K) are the electrolytes considered most important, as they are necessary to many biological functions. Electrolytes are atoms or molecules that carry either a negative or a positive charge. Anions have an extra electron, and thus carry a negative charge. Cations are missing an electron, thus they carry a positive charge. In the study cited, Kealy et. Al. Introduced the theory of "dietary anion gap" or DAG. ^[8] The researchers explained DAG as the amount of chloride ion subtracted from the sum of sodium ion and potassium ions:

DAG = [(K+ + Na+) - Cl-]

This experiment, consisting of the raising of 167 puppies, included puppies from five different breeds. They were placed on three different diets tat varied only in their DAG content. Examples of low DAG ingredients are rice with a DAG of 6 and corn gluten meal with a DAG of 5. The result of this experiment showed that except for some breed-specific exceptions, those dogs that were fed a lower DAG diet had better hips at 30 weeks than those fed a diet with a higher DAG content. Differences in DAG balance did not result in different rates of weight gain. This is important, for it allowed elimination of weight gain as a causative factor in the study. Hips were evaluated by their degree of subluxation as measured by the Norberg angle. The Norberg angle is the "angle included between a line connecting the femoral head centers and a line from the femoral head center to the crainiodorsal acetabular rim." ^[9] The greater the Norberg angle, the less the subluxation. Norberg angles are commonly measured as < 90 degrees for loose hips and > 105 degrees for tight hips. Those dogs with better hips at 30 weeks also had good hips at 2 years of age.

Unfortunately, the researchers were unable to explain the mechanism or the "why" of how they got the results they did. One of the theories proposed was that a lower DAG somehow affected the pH or "acidity" of the synovial fluid. This in turn affected the osmolality or "thickness" of the synovial fluid. The osmolality of a fluid depends upon the number of dissolved particles in it, and is the measure of the osmotic pressure. In previous studies, a higher osmolality was associated with the greater synovial fluid volume found in dysplastic dogs. Note, of course, that there is a normal range of DAG values in a balanced diet. Leaving that range while formulating a dog food, for example, could cause serious problems.

Calcium

The question of calcium supplementation while controversial among breeders, is fairly easy to answer: don't do it. It is not necessary to add extra calcium to your dog's diet. Not only is calcium an essential skeletal component, it is also necessary for blood coagulation, hormonal release and muscle contraction. The three biological systems involved in controlling the amount of calcium in the blood are bones, kidneys, and the intestine.

Calcium is constantly being recycled in and out of living bone. In the adult dog, under balanced conditions, both accretion (calcium uptake) and resorption (calcium loss from bone) values vary from 0.1 to 0.2 mmol per kilogram of body weight per day. [A millimole is a minute measure of molecular weight.] For the rapidly growing puppy these values are at least 100 times higher. ^[10] Another difference between an adult dog and a puppy is their relative abilities to absorb calcium from the food they ingest. In the adult dog, the percentage of calcium assimilated from food varies from 0 to 90 percent, depending upon the composition of the food and its calcium content. ^[11]

A 1985 study which examined the physical, biochemical and calcium metabolic changes in growing Great Danes, showed that young puppies do not have a mechanism to protect themselves against excessive calcium feeding. Under the influence of certain hormones, the calcium excess is routed to the bones. This results in severe pathological consequences for the patterning for the growing skeleton and the subsequent impairment of gait. Strongly correlated with high calcium intake is disturbed enchrondral ossification (growth plate anomalies) causing the clinical appearance of radius curvus syndrome and osteochondrosis (a disturbance of bone formation within the cartilage, occurring during periods of maximum growth). ^[12] Chronic, high calcium intake in large breed dogs has also been associated with hypercalcemia, elevation of the liver enzyme alkaline phosphatase, retardation of bone maturation, an increase in bone volume, a decrease in the number of bone resorption cells, and delayed maturation of cartilage. ^[13] We can safely conclude that calcium plays a significant role in skeletal disease. The giant breed dogs, because of their rapid and intense growth, are sentinels for nutritionally influenced diseases. These changes, while exaggerated in the giant breeds, are just as real-though they may be slower to surface and not as easily identified-in the smaller breeds.

Vitamin C

Vitamin C (L-ascorbic acid) has frequently made it into the literature along with calcium. At one time or another vitamin C has been touted by somebody as a cure-all for virtually any malady known to man and beast. This is not discount the requirements for vitamin C, for it is absolutely necessary. Fortunately for dogs, they produce an enzyme called L-gulonolactone oxidase, which allows them to synthesize vitamin C from glucose without having access to a dietary form of vitamin C. (A deficiency could only be the result of either a problem with absorption or an increased need.) Interestingly, canines produce only 40mg of ascorbate per kilogram of body weight, which is far less than other mammals with the ability to synthesize their own vitamin C. There is no established minimum daily requirement for vitamin C in canine nutrition. That said, let's look at the function of the vitamin C the dog manufactures.

Vitamin C figures prominently in the biosynthesis of collagen. ^[14] Collagen is an important structural protein in the body. There are different types of collagen, but it is Type I collagen that appears most often in connective tissue, particularly in bone and ligaments. Vitamin C adds an -OH group to the two amino acids proline and lysine. Without this functional group there is a decrease in the number of cross-links in collagen. Without this cross-linking, the melting temperature of the protein is reduced from about 39 degrees to 23 degrees centigrade. In other words, without the cross-links this protein can be denatured at body temperatures.

There is experimental evidence that vitamin C may play a role in bone mineralization by stimulating bone resorption. What has been shown by one researcher to be efficacious in treating the physical manifestations of canine hip dysplasia (CHD) is a form of vitamin C called polyascorbate. ^[15] Calcium ascorbate, used in conjunction with vitamin E, also is considered helpful in reducing the inflammatory processes that accompany the disease. In this form, vitamin C is taken up by the bone along with calcium, and this acts like a time release factor that keeps the blood plasma concentration high and the cells constantly "bathed" with vitamin C.

With all the continuing fuss about vitamin C in the fad literature, it was inevitable that it would be tried for treatment of hip dysplasia. Belfield (1976) conducted a somewhat anecdotal study on eight German Shepherd Dog litters of puppies from dysplastic parents or parents known to have produced dysplastic puppies. ^[16] Megadoses of ascorbate were given to dams (2 to 4 grams of sodium ascorbate crystals per day) and to the pups (birth to 3 weeks-calcium and vitamin E supplement; 3 weeks to 4 months-500 grams ascorbate per day; 4 months to 1.5 to 2.0 years-1 to 2 grams ascorbate per day). Belfield claimed that none of the pups developed hip dysplasia, and breeders involved with the research were so convinced that they guaranteed dysplasia-free puppies if the ascorbate therapy was followed by the new owner. It is significant to note that no follow-up studies were published. While this is interesting, there is little accepted hard evidence to suggest that supplementation with ascorbate can prevent or ameliorate canine hip dysplasia. Readers are cautioned that large doses of vitamin C are not considered mainstream prophylaxis or therapy. The truth of the matter is that it is in the genes, not the diet, though diet may play a minor part.

A recent study (1993) observed that synovial fluid volume as related to osmolality correlated highly with the incidence of hip dysplasia. ^[17] This suggested that the swelling of the joint capsule from excess fluid pressure might be forcing the femoral head out of position in the acetabulum.

Tissue changes

Before any radiographic indications appear, there are structural changes at the tissue level of muscles, ligaments and cartilage. Cellular changes and molecular changes occur both in the joint capsule and in the synovial fluid. One study suggested that one of the first observable changes of the disease process is hypertrophy or swelling of the pectineus muscle fibers. ^[18] This hypertrophy is thought to be a compensatory adaptation to extreme contractile tensions and may be the result of the muscle mass trying to hold the acetabulum and the femoral head in the proper position.

Another study showed that the composition of the pectineus muscle was significantly different between 2-month-old puppies that eventually developed normal hips, and those that were dysplastic by 24 months. ^[19] The two groups differed by the size of the muscle fibers, but this time, the dysplastic animals had smaller than normal muscle fibers (hypotrophy) and the ratio between contractile tissue and non-contractile tissue was lower. Thus, not only did the affected animals have diminished capacity to contract their muscles, their muscles were also less elastic. This study begs the question of joint laxity: Once stretched, would the muscles tend to remain stretched, thus resulting in a looser hip joint? Unfortunately, it cannot be said with any certainty whether these differences are causal or correlative.

It is certain, however, that hip dysplasia is characterized by joint laxity. ^{[20], [21], [22], [23], [24],} Whether such laxity is the result of the pathological processes involved in the disease, or whether the laxity is the cause of the disease, cannot be determined. Remember, however, that loose joints and hip dysplasia are found together. We will be coming back to this point in later articles. There is a little twist to what we find: All dogs that have hip dysplasia have loose hips, but not all dogs with loose hips have hip dysplasia. It is not known which comes first: remodeling of the bony surfaces leading to abnormal wear of articular surfaces and joint instability or vice versa. It may very well be that both processes are concurrent and/or iterative processes.

Other changes that can precede either clinical signs, like pain and gait abnormalities, or radiographic evidence of hip dysplasia include thickening of the joint capsule and swelling of the round ligament. Subtle and early changes in articular cartilage structure also precede clinical signs. Specifically, in affected animals, the ratio between Type A cells and Type B cells differs from the norm. Type A cells are macrophages, i.e., large mononuclear cells produced by the immune system which ingest damaged cells and blood tissue. Type B cells are fibroblasts which are precursors of connective tissue. In one study, the population of Type A cells increased. ^[25] Conceptually this makes sense, as the function of macrophages is to scavenge damaged cells, which would be the case if articular cartilage is being damaged. Note that these changes can only be observed after dissection and examination under an electron microscope. While diagnostic and predictive, such examination is without use to the clinician who is trying to diagnose the disorder. What is important to remember is that these changes are found in dogs whose x-rays showed them to be perfectly normal at the time of radiographic study. As a concerned breeder or fancier of dogs, this should alarm you. Do not be too alarmed, however, because there is hope for predictive techniques. These will be covered in later articles in this series.

Significant studies

The major study demonstrating the polygenic and multifactorial aspects of canine hip dysplasia is probably the 1991 German study an German Shepherd Dogs. ^[26] Unfortunately this article is in German and we know of no translations available. While this poses no problem for co-author Thorpe-Vargas, as she used to be at the Max Planck Institute in Germany, it is a real problem for co-author Cargill, as he has to take her word for it, supported only by Medline abstracts in English! The importance of this study is that it covered 10,595 dogs. Furthermore, this study attempted to quantify both environmental influences and genetic influences on the frequency of hip dysplasia. Models were developed using the following variables-independent random variables: age at X-raying, birth year, season, litter size, percent of X-rayed dogs in each litter and sex ratio of litter; independent fixed variables: sire and dam.

Through multiple linear and non-linear regression methods it was shown that sire, dam, sex and age at X-raying all showed statistically significant influence on the occurrence of hip dysplasia. The heritability indices (H²) were-Relationship: full siblings, H² = 0.30; maternal half-siblings, H² = 0.48; and paternal half-siblings, H² = 0.11.

The researchers' caveat at the end of the study was that only the paternal half siblings' heritability index should be accepted because kennel and breeder effects are confounded with the dam effect. Their overall conclusion was that the frequency of hip dysplasia could be reduced if selection for breeding based upon the estimation of breeding values (H²) with respect to the frequency of hip dysplasia in allrelatives was implemented.

Many of the world's militaries are good sources of information on German Shepherd Dogs. The goals of such organizations have been to improve behavioral traits and to reduce the frequency of CHD. One of the more interesting studies in the literature is the one based uopn information provided by the US Army's division of Biosensor Research on the German Shepherd Dogs bred between 1968 and 1976.^[27] Detailed records were available for 575 animals representing 4 years, 18 sires, 71 dams and 48 human handlers. Variance component estimates were made, which allowed estimates of the heritabilities for both temperament and CHD scores to be made. The heritability index (H²) for temperament was 0.51 and for CHD was 0.26. Interestingly, in this population the genetic correlation between good temperament and bad hips was -0.33. Given the selection process of the U.S. Army, it was not surprising to find that dogs with good temperaments also had good hips. Because of the extremely high heritability index for temperament, records of the animal being evaluated can be used for repeat breeding selection rather than the records of the progeny.

A 1993 Austrian dissertation looked at a population of 10,750 Hovawarts from 1962 to 1988, out of which CHD findings were available for 4,387 dogs. ^[28] The goal of the dissertation was to statistically calculate two parameters. The first was a prediction coefficient based upon the CHD findings of all the ancestors of a specific animal. The second was a "taint" coefficient calculated on the basis of the CHD findings of all ancestors as well as of the individual CHD finding as well as those of any offspring already checked for CHD. The conclusions of this dissertation were that both the "prediction" and "taint" coefficients were useful in calculating the relative CHD risk of the prospective offspring when selecting breeding partners. A connection was found between the CHD findings and the inbreeding level of an animal as calculated from the "ancestor loss coefficient" and Malecots "coefficient de parente." Thus, increasing levels of inbreeding increase the risk of CHD. There was no difference between males and females for risk of CHD. Detailed coverage of the various genetic coefficients is beyond the scope of this article. Readers are directed to modern comprehensive texts, dissertation abstracts and the like in genetics should more than a passing familiarity with the intricacies of these coefficients be required.

Conclusions: While environmental effects, to include nutrition and exercise, may play a part in mitigating or delaying the onset of clinical signs and clinical symptoms hip dysplasia remains a genetically transmitted disease. Only by rigorous genetic selection will the incidence rate be reduced. In the meantime, it makes sense to have lean puppies that are exercised regularly and to avoid breeding any animals from litters that showed signs of hip dysplasia. It is probable that even normal exercise levels may increase the phenotypic expression of CHD of a genetically predisposed dog. Stay away from calcium supplementation of any kind; all it can do is hurt. There is no conclusive evidence tat vitamin C can prevent hip dysplasia, but there is some evidence that vitamin C may be useful in reducing pain and inflammation in the dysplastic dog. Let your conscience and your veterinarian be your guides in supplementing with vitamin C. Fortunately, large doses of vitamin C are readily excreted, but it is still possible to cause untoward side effects with megadoses.

The next article in the series will address the abnormal hip, to include differential diagnosis, observation, palpation fluid sampling and sedated and unsedated radiographic studies.

Credits

References

^[1] Hanssen I. "Hip Dysplasia in dogs in relation to their month of birth." Vet Rec. 1991 May 4;128(18):425-6.
^[2] Kealy R.D., Olsson S.E., Monti K.L., Lawler D.F., Biery D.N., Helms R.W., Lust G., Smith G.K. "Effects of limited food consumption on the incidence of hip dysplasia in growing dogs." J Am Vet Med Assoc. 1992 September 15;201(6):857-63.
^[3] Kealy R.D., Olsson S.E., Monti K.L., Lawler D.F., Biery D.N., Helms R.W., Lust G., Smith G.K. "Effects of dietary electrolyte balance on subluxation of the femoral head in growing dogs." Am J Vet Res. 1993 April:54(4):555-62.
^[4] Cargill J.C. "Feed That Dog! Part II." Dog World. 1993 August;75(8):12.
^[5] Ibid.
^[6] Ibid.
^[7] Ibid.
^[8] "Effects of dietary electrolyte balance." Pp. 555-62.
^[9] Smith G.K., Gregor T.P., Rhodes W.H. Biery D.N. "Coxofemoral joint laxity from distration radiography and its contemporaneous and prospective correlation with laxity, subjective score, and evidence of degenerative joint disease from conventional hip-extended radiography in dogs." Am J Vet Res. 1993 July;54(7):1023.
^[10] Hedhammer A., Wu F.M., Krook L., Schryver H.F., de Lahunta A., Wahlen J.P., Kallfelz F.A., Nunez E.A., Hintz H.F., Sheffy B.E., Ryan G.D. "Overnutrition and skeletal disease. An experimental study in growing Great Dane dogs." Cornell Veterinarian 1974;64 supp15:11-160.
^[11] Hedhammer A., Krook L., Schryver H.F., Kallfelz F. "Calcium balance in the dog." In "Nutrition of the Dog and Cat" ed. Anderson R.S.; Pergamon Press, Oxford 1980:119-27.
^[12] Hazewinkle H.A.W. "Influence of different calcium intakes on calcium metabolism and skeletal development in young Great Danes." PhD Thesis Utrecht State University 1985.
^[13] Hazewinkle H.A.W., Goedegbuure S.A. Poulos P.W., Wolvekamp W.ThC. "Influences of chronic calcium excess of the skeletal development of growing Great Danes." J Am An Hosp Assoc. 1985;21:377-91.
^[14] Berg R.A., Prockop B.J. "The thermal transition of a non-hydroxilated form of colagen: Evidence for a role for hydroxiproline in stabilizing the triple helix of collagen." Bio Chem Bio Phys Res Commun. 1973; Vol. 52:115-129.
^[15] Berge, G.E. "Polyascorbat, et behandlings-alternativ ved kroniske forandringer I stotte og bevegelsesapparetet hos hund" ("Polyascorbate, an interesting alternative by problems in the support and movement apparatus in dogs.") Norsk Veterinaertidsskrift (Norwegian Vet J), August/September 1990;102:581-582.
^[16] Belfield, W.O. "Chronic subclinical survey in canine hip dysplasia." Vet Med Sm An Clin. 1976; Vol. 71:1399-1403.
^[17] Lust G., Beilman W.T., Rendanom V.t. "A relationship between degree of laxity and synovial fluid volume in coxofemoral joints of dogs predisposed for hip dysplasia." Am J Vet Res. 1980,41:55-60.
^[18] Cardinet, G.H. III, Wallace L.J., Fedde M.R. "Developmental myopathy in the canine." Arch Neurol. 1969, 21:620-630.
^[19] Lust G., Craig P.H., Ross G.E. "Studies on pectineal muscles in canine hip dysplasia." Cornell Vet. 1972, 62:628-645.
^[20] Henricscon B., Norberg I., Olsson S.E. "On the etiology and pathogenesis of hip dysplasia: a comparative review." J Small Anim Pract. 1966;7:673-687.
^[21] Smith G.K., Biery D.N., Gregor T.P. "New concepts of coxofemoral joint stability and the development of a clinical stress radiographic method for quantitating hip joint laxity in the dog." assoc. med vet am j 1990 January 1;196(1):59-70.
^[22] "Coxofemoral joint laxity." Pp.1021-1042.
^[23] Morgan S.J. "The pathology of canine hip dysplasia." Vet Clin N.Am Sm Anim Pract. 1992 May;22(3):541-50.
^[24] Alexander J.W. "The pathogenesis of canine hip dysplasia." Vet Clin N.Am Sm Anim Pract. 1992 May;22(3):503-11.
^[25] Greisen H.A., Summers B.A., Lust, G. "Ultra Structure of the Articular Cartilage and Syunovium in the Early Stages of Degenerative Joint Disease in Canine Hip Joints." Am J Vet Res. 1982; 43:pp. 1963-1971.
^[26] Distl O., Grussler W., Schwarz J., Karusslich H. "Analyse umweltbedingter un genetischer Einflusse auf die Haufigkeit von Huftgelenksdysplasie beim Deutschen Shaferhund." ("Analysis of environmentally conditioned and genetic influences on the frequency of hip joint dysplasia in German Shepherd Dogs"). Zentralbl Veterinarmed A. 1991 Jul;38(6):460-71.
^[27] Mackenzie S.A. "Inheritance of temperament and hip dysplasia scores in German Shepherd Dogs." 1984 March; Dissertation Abstracts International-B 44/09, p.2652.
^[28] Potscher L.A. "Selektion gengen hueftgelenksdysplasies (HD) in einer Hovawart population" ("Selection criteria concerning hip dysplasia (HD) in a Hovawart population.") 1993 Winter; Dissertation Abstracts International-C 54/04, p.1069.

Links

Dog Genome Project, A scientific study of the chromosomes in dogs. Also information about genetic disorders in dogs.

Next, go to Part III

Purebred Dog Breeds into the Twenty-First Century
Achieving Genetic Health for Our Dogs

By J. Jeffrey Bragg, Seppala Siberian Sleddogs, Canada.
The article was originally published at: http://www.seppalakennels.com/articles/purebred-dog-breeds-21st-century1.htm

1. What is a Canine Breed?
2. The Origins of Dog Breeds
3. The Healthy Continuation of Breeds
4. The Fallacy of Breed Purity
5. The Demise of Typological Thinking
6. Abandoning Natural Selection
7. A Century of Nineteenth-Century Dog Breeding
8. Lessons from Population Genetics
9. The Crux of the Problem
10. An Example from One Breed
11. The Holistic Breed
12. New Structures for the Dog Fancy
13. A Healthy Balance for Breed Identity
14. Can it Really Work?
15. A Canine Revolution?
16. Postscript
17. Bibliography
18. Glossary
19. Afterword

What is a Canine Breed?

What is a breed? To put the question more precisely, what are the necessary conditions that enable us to say with conviction, "this group of animals constitutes a distinct breed?"

In the cynological world, three separate approaches combine to constitute canine breeds. Dogs are distinguished first by ancestry, all of the individuals descending from a particular founder group (and only from that group) being designated as a breed. Next they are distinguished by purpose or utility, some breeds existing for the purpose of hunting particular kinds of game, others for the performance of particular tasks in co-operation with their human masters, while yet others owe their existence simply to humankind's desire for animal companionship. Finally dogs are distinguished by typology, breed standards (whether written or unwritten) being used to describe and to recognise dogs of specific size, physical build, general appearance, shape of head, style of ears and tail, etc., which are said to be of the same breed owing to their similarity in the foregoing respects.

The preceding statements are both obvious and known to all breeders and fanciers of the canine species. Nevertheless a correct and full understanding of these simple truisms is vital to the proper functioning of the entire canine fancy and to the health and well-being of the animals which are the object of that fancy. It is my purpose in this brief to elucidate the interrelationship of the above three approaches, to demonstrate how distortions and misunderstandings of that interrelationship now threaten the health of all of our dogs and the very existence of the various canine breeds, and to propose reforms which will restore both balanced breed identity and genetic health to CKC breeds.

In order for canine breeds to fulfil their destinies effectively, the three distinct axes along which breeds are distinguished must have equal importance and consideration, otherwise serious problems arise. Breeds cannot be distinguished by ancestry alone, by purpose alone, or by typology alone. Unless these three vectors of breed identity interrelate fully and co-operatively, the fulness of that identity is missing or marred. Unfortunately, this full and co-operative interrelationship is a rarity in our contemporary dog world. The criteria of ancestry are applied rigidly and mechanically; the criteria of purpose and utility are subordinated or not considered at all; the criteria of typology are applied in a highly exaggerated, obsessive fashion. The interaction of the three approaches is seldom considered and almost never is a sustained effort made at the integration of the three.

The Origins of Dog Breeds

Canine breeds come into existence in many different ways and their beginnings are very often shrouded in obscurity. Let it not be thought that the three or four hundred-odd dog breeds now extant are the only ones possible, or that there cannot be any more truly new breeds. Such is the genetic plasticity of the dog that there is no end to the possible unique variations of which the species is capable. New breeds are born and old breeds die periodically. The genetic transformation of the dog goes on ceaselessly, and for that reason it is impossible that any breed should remain frozen, with all its characteristics fixed and unchanging, for any appreciable length of time. It must be realised that canine breeds are manmade, created by artificial selection out of the endless diversity of the canine gene pool. Breeds must not be confused with species or even subspecies, which occur naturally under the influence of natural selection; dog breeds are only unstable manmade varieties which would not survive unchanged in the natural world without human management.

An important characteristic of breeds is that they are created by breeders -- not by registries or protective organisations such as The Canadian Kennel Club. The origin and course of a canine breed is in the hands of its breeders, first, last and always. It is the business of cynological associations to facilitate and support the work of dog breeders and not vice versa. The purposes of the Animal Pedigree Act, under which CKC is incorporated, are the promotion of breed improvement and the protection of those who breed and purchase animals; such is the mandate of the Act and therefore of the Club (Animal Pedigree Act, Section 3(a,b) ). All else is secondary.

Ordinarily a breed has already existed for an appreciable length of time before it reaches the point of becoming a recognised breed served by a registry. Nonetheless, the event of its "recognition" by a registry such as CKC is always a crucial one in the history of a breed. As things now stand, breed recognition is far more crucial (and ultimately damaging to the welfare of the animals) than it need be or ought to be, but more of that anon. First let us examine what is needed to start a new and unique canine breed.

Four essential characteristics usually distinguish the origin in the genetic sense of a new breed (as opposed to the discovery, popularisation and "recognition" of, for example, an autochthonous breed which may have existed in a particular region for a long time without connection to formal cynological structures). The first and most crucial characteristic is the founder event, in which a finite number of individual canines is chosen to contribute genetic material to found a new and unique canine population. They may all be quite similar, or they may be widely divergent one from another (as when Bulldog and Mastiff specimens were used to create the Bullmastiff breed). What matters is that a finite and sometimes quite small number of individuals are selected from the existing canine population and set apart so that their genetic material alone forms the gene pool for the new breed. That is in fact the next characteristic: isolation. If the founder group continues to exchange genetic material at random with the general canine population, a new breed will not result. Without genetic isolation of the new founder group, the differentiation that creates a new breed cannot take place. The logical consequence of this isolation is the next characteristic: inbreeding. If the founder group is of small or moderate size, such inbreeding cannot help but occur. Even if the founder group should be quite large, ordinarily those who guide the breeding which creates the new breed will find it necessary at some stage to employ a strong degree of incest breeding or inbreeding, to facilitate the weeding-out of undesired characteristics and the fixation of desired traits. Particularly if individuals of widely divergent type and physique are involved, inbreeding will be required to set up a stable genome in which random variability is kept within limits defined by the breeders. The final essential factor is artificial selection, since inbreeding alone will not serve to fix type characteristics and to eliminate unwanted traits. The breeders must select among the individuals produced in early generations so that only those displaying the desired characteristics are allowed to produce subsequent generations. Without the four factors of the founder event, isolation, inbreeding and artificial selection, new breeds ordinarily do not come into existence. These four tools are used to define a new genome which, hopefully, contains only the traits desired by the creators of the new breed and is able to reproduce itself, with its distinguishing characteristics, to a fair degree of stability and consistency.

The Healthy Continuation of Breeds

Purebred dogdom is even now in serious trouble through a general failure to distinguish between what is necessary to establish a breed and what is desirable to continue that breed in perpetuity. Most registered breeds are less than a century old qua registered breeds; many are but fifty or sixty years old. Yet nearly all breeds now show levels of expression of genetic defects that must be considered unacceptable. Over 500 distinct genetic defects have been catalogued in various breeds of purebred dogs and more continue to come to light regularly. Some of these have reached very high levels of incidence, creating problems for breeders and dog owners, threatening the health of entire breed populations. What is worse, in many instances organised control programmes seem relatively ineffective. Although such programmes successfully identify affected animals, in some cases individuals with several generations of "clear" ancestry stubbornly continue to produce affected stock. Let us try to examine what has gone wrong and what must be done to correct the situation.

First of all it must be recognised that practices which were essential for the differentiation and establishment of a new breed may not necessarily be desirable for its continuation over time and may in fact be prejudicial to a breed's continued existence over the long term.

Let us take isolation, for example. Without genetic isolation, it would not be possible to control the genome of a new breed still few in number. It takes time and careful breeding to fix a new combination of characteristics; while that is being done, the regular addition of new genetic material would generally be counterproductive. Yet in the long term, if genetic isolation is maintained, it will necessarily lead to degeneration through genetic drift. Similarly inbreeding, if it continues to be practised after the need for it is past, will lead to a steadily increasing state of homozygosity which may well destroy the genetic health of the new breed. Even artificial selection, if carried on too strongly for too long, can combine with isolation and inbreeding to reduce drastically the effective breeding population, thus eroding the genetic health of the breed.

The Fallacy of Breed Purity

The present structure of The Canadian Kennel Club's studbook registry (and others like it) embodies a fallacy which is directly responsible for the current genetic crisis in purebred dogs: the fallacy of breed purity. The ideal of the purified lineage is seen as an end in itself; accordingly, the studbook has been structured to reflect and to enforce that ideal rigidly and absolutely. This insistence on absolute breed purity arises from nineteenth-century notions of the "superior strain" which were supposedly exemplified by human aristocracies and thoroughbred horses; this same ideal, pushed to an illogical conclusion on the human plane, resulted in the now discredited "scientific racism" of the Nazis, who tried through selective human matings to breed an Aryan superman. The idea of the superior strain was that by "breeding the best to the best," employing sustained inbreeding and selection for "superior" qualities, one would develop a bloodline superior in every way to the unrefined, base stock which was the best that nature could produce. Naturally the purified line must then be preserved from dilution and debasement by base-born stock. There is no support for this kind of racism in the findings of modern genetics -- in fact, quite the opposite: population groups that are numerically limited and closed to new genetic inflow are now thought practically certain to be genetically inferior. Certainly towards the close of the nineteenth century it became embarrassingly obvious that the human aristocracies of Europe were degenerating rapidly under their own version of the "closed studbook."

The ideal of breed purity as applied to purebred dogs has resulted at the end of the twentieth century in a subculture that holds "purebred," registered animal stock to be qualitatively superior to crossbred or "mongrel" stock. (The word "mongrel" is in fact part of the vocabulary of racism, being applied equally to canine stock of no recognisable breed, to animal crossbreeds, and to persons of mixed race!) In this subculture -- presided over in Canada by the CKC -- it is thought to be of paramount importance that purebred stock be maintained unsullied by any genetic influence external to the supposedly superior strains that are produced by registered breeding in a closed studbook from a small group of foundation stock. New members of the CKC are required to subscribe to "Conditions of Membership" whereby they promise to have nothing to do with "dogs which are not purebred" (with the exception of family pets and boarders), "purebred" being specifically defined as referring only to dogs "registered individually or eligible for registration in records of the CKC." Litters which are made the subject of complaints that they may not be purebred are investigated and in many cases ceremoniously withdrawn from the registry by resolution of the Club's Board of Directors. Whether you like the word or not, this is effectively a special variety of racism in concept and in practice.

Not all dog breeders are in agreement with the proposition that breed purity is more important than anything else, particularly when they are confronted with the problem of breeding dogs to demanding performance standards. Mostly such dissenters are obliged to carry on their breeding without the benefit of centralised pedigree record keeping and official certificates of registration -- for example, those who breed "alaskan huskies," the high-performance racing sleddogs that dominate both short and long-distance dogsled racing, keep pedigree records and maintain sophisticated breeding programmes, but only as individual breeders. Yet sometimes even participants in established purebred registries engage in a subtle kind of rebellion, quietly breeding according to their own judgment in defiance of formal restrictions. Thus the Racing Greyhound Club of Australia, when it recently subjected a broad sample of stock from its registry to DNA testing, is rumoured to have discovered that many pedigrees failed to match DNA ancestry findings and that considerable interbreed crossing had apparently occurred. Similarly most Siberian Husky fanciers are aware that some CKC bloodlines may have received surreptitious infusions of genetic material from non-purebreds or from other breeds. In some circles one even gets the distinct impression that "it's OK to crossbreed occasionally if you have a good reason for doing it and you manage it in such a way that no embarrassingly obvious mongrels are produced" -- i.e., "just don't get caught!" Thus the sanctity of breed purity may sometimes be less than inviolate in actual practice.

Population geneticists insist that limited populations under strong artificial selection, subjected to high levels of incest breeding -- such as our own CKC purebreds -- simply cannot maintain genetic viability and vigour in the long term without the periodic introduction of new and unrelated genetic material. They are referring, moreover, to true outcrossing, the introduction of stock unrelated to the breeding line, not merely the use of a dog which might be from someone else's kennel but is derived from exactly the same foundation stock some generations back.

The Demise of Typological Thinking

DNA research has radically changed zoological concepts of species, subspecies and varieties. In the nineteenth century and the first half of this century it was thought that a species could be represented by a type specimen, that the vast majority of individuals of a species were virtual photocopies of the type specimen, genetically speaking, and that the genetic norm for most species was homozygous at most loci. In the mid-1960s the credibility of that idea was shattered as electrophoresis protein studies revealed extensive protein polymorphism that had not been previously suspected (Carson, 1983). Today the concept of a species in a satisfactory state of genetic health invokes a state of "dynamic balance" in which the species genome contains an array of genotypes with a high degree of heterozygosity, with multiple alleles at many gene loci. Natural selection is now thought to favour heterozygotes in a way which tends toward a high state of natural variability, preserving the greatest variety of possibilities with which a species can meet new environmental challenges. Conversely, species which have lost most of their genetic diversity, often through accidental population "bottlenecks" similar to those which regularly occur in purebred dogs, are held to be in high risk of extinction through the loss of adaptive capability. (The most notorious example is the cheetah, which is almost totally homozygous and is thought to have undergone at some time a bottleneck reducing its population to a tiny handful of specimens.)

There is no reason why dog breeds also cannot be maintained in a balanced state of heterozygosity, analogous to that of healthy wild animal species, if typological thinking in the dog fancy could somehow be replaced (or at least tempered) with population thinking. Fanciers will generally admit that no dog conforms perfectly to its breed standard. Thus the concept of the perfect type specimen, to which an entire breed ought to conform as closely as possible, is really as foreign to dog breeds as it is to animal species in the wild.

The fanatical pursuit of breed type to the exclusion of other more important factors (more important to the dog, to his owner, and to his veterinarian) has led to a distinctly unhealthy situation in most breeds. Since the majority of breeders within CKC seem to direct their efforts toward the production of a winning exhibition specimen, and since many breeders therefore breed their females to the males that do the most winning at dog shows, a situation has arisen in which continued effort to produce show winners leads consistently to greater and greater exaggerations of "type," that being the factor most susceptible to the off-the-cuff three-minute analysis of the breed ring. It is an accepted fact that strong incest breeding is the fastest route to this kind of "success"; here is one successful show breeder's recipe for "excellence" (de Boer and de Boer, DOGS in Canada, April 1994):

"My approach would be to identify an outstanding, dominant stud dog. Let's call him 'Shadrack.' To improve the odds, I'd buy or lease three bitches whose grandsire on the dam's side was the same as Shadrack's sire. Let's call the grandsire 'Fashion Hint.' I would breed the Fashion Hint bitches to Shadrack.

"Assume, in this first generation, that I get three nice bitches. For the second generation, I'd breed them to a half-brother of these three bitches (Shadrack's son, also a dominant sire). For the third generation, several 'mix and match' options include going back to Fashion Hint or Shadrack. I could also do brother-to-sister or father-to-daughter breeding."

Thus the quest for more and more refined breed type leads directly to a state of advanced homozygosity, rising inbreeding coefficient, low effective breeding population and consequent impoverishment of the gene pool in most CKC breeds, through rampant uncontrolled incest breeding.

The show ring has also been largely responsible for the decline of breed purpose, working ability and temperament in a great many breeds, notably sporting breeds, herding breeds and sleddog breeds. The quick and easy gratification of blue ribbons and gilt trophies all too readily supplants the hard work necessary to preserve and advance canine working abilities. If our dog breeds are to conform to the ideal of "a sound mind in a sound body" (as advocated by the proponents of the Advanced Registry), the fancy must find some way of ensuring that less dog-breeding takes place along the lines of least resistance and cheap gratification, so that greater attention is paid to working characteristics, temperament and trainability. A balanced outlook on breed identity must be restored by integrating canine function with the ideals of conformation, beauty and "type." All kinds of dogs, toy breeds not excepted, can perform useful functions and respond to training. Those aspects of the fancy should be accorded an importance at least fully equal to that of type and conformation instead of being regarded as merely optional. For example, breeding and exhibition of utility breeds such as gundogs and sleddogs merely for sale as pets and for dog shows, with no effort made to maintain and advance their working capabilities, is an obvious abuse which must lead inevitably to mental and physical degeneracy in those breeds.

Abandoning Natural Selection

The breeder of domestic stock often assumes that he has abandoned the realm of natural selection and that only artificial selection plays a significant role in his breeding programme. Nothing could be further from the truth. The breeder may attempt to abandon natural selection; natural selection, however, will not abandon his stock. As one geneticist puts it:

... Man-imposed characteristics, however, like the flower colours and forms selected by the plant breeder, usually do not perturb the deep-set genetic variability systems of the species. Most such changes are reversible when a less restricted gene pool is restored. The 'balance' system appears to be retained by natural selection, which, perhaps paradoxically, pervades most systems of artificial selection.

--Hampton L. Carson, The Genetics of the Founder Effect, 1983

Those who attempt to set aside the balanced genomes arrived at by natural selection must struggle thereafter to attain and to maintain fitness in their stock. There is more to this than mouthing platitudes about "soundness." Artificial selection alone, such as that used to produce winning exhibition dogs, involves breeding in a way which flagrantly disregards most of the gene loci in the canine genome. Since genes assort in groups on chromosomes (a phenomenon known as "linkage"), inbreeding and selection for desired traits of superficial appearance unavoidably affect many other genes which are inadvertently selected and often fixed in a homozygous state in total ignorance of what is happening. This may be a major factor in the current prevalence of genetic diseases. Thus natural selection, baulked for a season by artificial selection, high-level nutrition, and advanced veterinary care, reasserts its primacy at a deeper and more serious level when the new genome as set up by the breeder proves flawed through genetic unsoundness, so that healthy and hardy animals can no longer be produced, however typey and attractive to the eyes of the judges the result may be.

Declining vigour caused by the inadvertent fixation of sublethal and subvital alleles will not be made up for by breed points. Fitness criteria may not be replaced with impunity by aesthetic criteria. The animal's environment is the ultimate arbiter of its fitness and will not be denied its say. You may vaccinate the dog and dose him with antibiotics, feed him with vitamins and minerals as you like, enclose him in a sterile pathogen-free laboratory environment if it comes to that! Still natural selection may not be avoided; it only emerges at a deeper level. In a sense the dog's environment includes his own physical body; if the genes which blueprint his physiology are flawed, then the dog is doomed regardless of his beauty and classic breed type. The truth is that the "superior strain" cannot be produced by manmade breeding programmes and artificial selection; the breeder's decisions are subject to nature's veto at all times.

With what, then, will the breeder replace natural selection? If he replaces it with profit, the degeneracy of his stock will in the end put him out of business as veterinary costs and death eat up his profit margin. If he replaces it with beauty contests, in the end his beautiful contest winners will engender weaklings and degenerates. If he replaces it with screening programmes for the "elimination of genetic defects," in the end his stock will succumb to inbreeding depression as bitches fail to whelp naturally and puppies die in the nest. If he replaces it with veterinary care, in the end his stock will die prematurely of incurable cancer, or the young will fall prey to viral diseases despite repeated polyvalent vaccinations. If he replaces it with work and austerity, his stock may endure awhile longer, but in the end it will turn out to be afflicted with genetic ills that slipped through his demanding programme, or its performance will mysteriously decline as the inbreeding coefficient creeps upward. In the end, natural selection cannot truly be replaced with artificial criteria. The breeder must find a way to work with natural selection, within the framework of what is now known about the biological operation of the natural world. We in the canine fancy must begin to take lessons from wildlife biologists, from evolutionary biologists, from population geneticists.

In our quest for breed purity, the superior strain, and classic type, we have made a sad mess of our dogs -- with unhappy, neurotic temperaments, epilepsy, blindness, deafness, immune system weakness, skin diseases, blood disorders, endocrine system malfunctions, crippling bone disorders, deliberate deformity, and often even the inability to reproduce their kind without breeder and veterinary intervention. How clever we have been!

Can we not now take a clear-sighted view, as the millennium turns slowly over, of what we have done -- of our own pitifully-flawed creation in our world of purebred dogs and, like mature, intelligent people, clear away the mess and try to do better? Can we not learn from bad experience? If we would be truly clever, we might attempt to imitate more closely the methods of nature, to work within the natural system, albeit for our own ends. That would indeed be clever. I think that that is now possible, if we would but step outside our own incestuous little purebred world and learn something of what people working in other zoological fields of endeavour have already learnt.

A Century of Nineteenth-Century Dog Breeding

How, then, may we set about correcting the accumulated errors of over a century of what we might call nineteenth-century dog breeding? First of all it might be wise to attempt a short-list cataloguing the errors and abuses of which we are aware, the areas known to be deficient in one way or another.

• Dog shows must come high on the list. They began as an arena for the evaluation of breeding stock, they continued in the form of the "bench show" as a public showcase for purebred dogs. Both functions are now ill-served if not virtually abandoned. Championship shows are now just that, mills for the production of Champions, Best in Show and Group winners, little more. They contribute almost nothing to the true welfare of dog breeds; they have few lasting positive values to offer breeders, only ephemeral fads and fashions.
• Breed purpose and the cultivation of canine utility have a low status in the fancy, compared to what one author called "the glitz and hype of the show world." Those who concern themselves with the working ability of their dogs exist mostly in ghettos where little communication takes place with other branches of the fancy.
• Obedience work, begun as a way of initiating dog owners into the fascination and technique of training one's pet to be a pleasant, well-behaved companion, has become largely ritualised and sterile. The pursuit of "Club 200" (the perfect point score) has become an obsession. Intelligent and useful training on the owner's part, intelligent obedience on the dog's part, are now beside the point. What matters all too frequently now is the minutely-perfect performance of a set ritual. Here again we find a canine ghetto.
• The worship and exaggeration of type, as already noted, is responsible for a multitude of ills.
• Modern registries based on a rigidly-closed studbook are throttling the genetic health of all registered dog breeds. Genetic impoverishent is now a real and present threat. Many breeds now bear a genetic load of defects which has grown totally unmanageable as their respective gene pools have become more and more narrow through imprudent breeding and selection practices.
• Incest breeding, once a convenient tool for the rapid fixation of type in newly-registered breeds, has become virtually standard practice for those who seek success in dog breeding. The net effect has been the decimation of gene pools, widespread homozygosity and the unintended fixation of unknown scores, hundreds or thousands of alleles, many of which are proving to be harmful or lethal to the animals that bear them.
• The CKC, born in the height of the Victorian era, seems to cling to cumbersome structures, making it difficult for the Club to respond in a timely fashion to external challenges or internal needs. The entire By-Law and Amendment structure could do with modernisation. Many members feel there is little justification for such practices (for example) as the three-year member apprenticeship proviso, under which new members (or old ones who for whatever reason have let their membership lapse for a year or more) are completely disenfranchised for anywhere from three to five-plus years (inasmuch as elections and referenda are triennial), costing the Club dearly in lost members and wasted talent. Many members also feel that Board of Directors initiatives are frequently arbitrary and undertaken hastily with insufficient grass-roots consultation, while initiatives from the general membership must go through a slow and cumbersome multi-stage routine before they can be acted upon. One feels a general atmosphere within the Club of elitism and ultra-conservatism, as if those in power felt that only they themselves, the "old hands," knew what is good for purebred dogs and the fancy, and that newer members should not be entrusted with the franchise.
• Breed clubs seem to possess little real power to represent breeders or their breeds effectively. Special measures which they may feel essential for the health, development, and protection of the breeds whose breeders they represent must be put through the centralist CKC system and approved by the Board before they become effective; often such measures have little chance of approval because they are felt to conflict with the rigid all-breed norms of the Club. Since breed clubs have relatively little real power, they often tend to be less than fully representative of all breeders of a particular breed. Frequently they are more or less run by cliques; they waste much time and effort in wrangling and personalities, being perhaps inadequately supervised and not taken terribly seriously.
• Breeders, as well, are sometimes far from free to make their own responsible decisions for the best interests of their own dogs and bloodlines, being closely constrained by CKC By-laws and by the Animal Pedigree Act. Little discretion is given them regarding matters such as the withholding of registration papers, delaying registration of stock until it reaches physical maturity, the introduction of new genetic material when in their judgment it is needed for genetic health, etc.

Many of the abuses and deficiencies not rooted in outmoded attitudes such as racism and elitism arise from misunderstandings of genetic realities. Let us now examine briefly a few points of up-to-date genetic theory as they relate to purebred dog populations.

Lessons from Population Genetics

Gene Frequencies

Much of the work of population genetics involves estimating or calculating gene frequencies, which quantify the relative commonness or scarcity, within a particular population, of alleles at a particular gene locus. If there is only one version of a gene in the population, then the entire population is necessarily homozygous for that gene. Gene frequencies are expressed as decimal fractions which must add up to unity, so a gene without alternative alleles has a frequency of 1.0. The gene frequency figure is a ratio of the number of copies of alternate versions of a gene in the population, independent of the number of animals involved and of whether they have the gene in homozygous or heterozygous form. An individual may have two copies of the same allele or it may have one or none. For example, if a locus has two alleles, and the population involved consists of fifty animals, and there are 25 copies of one allele, then the frequency for that allele is 0.25; therefore the frequency of the other allele must be 0.75, with 75 copies of it in the same population. It must be emphasised that gene frequency by itself says nothing about relative heterozygosity or homozygosity; it deals only with quantitative aspects of alleles in the population, not the diploid genotype of individuals.

Founder Events

Perhaps the most crucial concept in population genetics for dog-breeders is the founder event, for its theory describes perfectly what takes place when a breed is "recognised" by CKC or a similar registry. Whatever may be the state of genetic balance or the frequency with which particular alleles are found in the general canine population, it all changes when a founder event occurs. In nature such events happen when individuals of a species occupy and reproduce in territory new to the species, losing contact with the source population of the migrants (as when small birds are deposited by hurricane winds on mid-ocean islands). The founder event describes the establishing of a small population, although later on it may grow to be a large one. When a finite number of individuals found a new population group, the genome of the new group will necessarily reflect the genes brought to it by the founder animals; gene frequencies within that population will reflect the gene frequencies within the founder group rather than that of the source population. In this way, when a founder event occurs, a gene quite rare in the source population may have a much higher frequency in the new population; conversely, genes common in the source population may be infrequent or even absent from the new population. It all depends on the genes of the founders! Thus a genetic defect extremely rare in the overall canine population can come to be common in a particular breed simply because one or more individuals of a small breed foundation carried that gene.

Hardy-Weinberg Principle

The Hardy-Weinberg Principle states that under certain specific conditions (random mating, very large population group, no mutations, absence of selection pressure, for example), the relative allele frequencies of genes at a given locus will not change from generation to generation and can be described by an equation, allowing the geneticist to create a mathematical model of gene frequencies within the population. Without trying to explain the equation and its operation here, we can still say in general that the net result is that heterozygote organisms will be much more numerous than homozygotes in a Hardy-Weinberg population. Many natural populations can be described in this way, although purebred dog populations cannot, since they are subject to inbreeding, artificial selection, non-random mating and small populations. Nonetheless, the principle has a certain significance, in that the overwhelming preponderance of heterozygotes in natural populations means natural selection tends to favour the heterozygote. Thus the natural genetic balance systems of most species include a high degree of heterozygosity (Carson, 1983). When we as dog breeders use incest breeding and artificial selection to fix characteristics arbitrarily, we are therefore quite likely to upset the natural genetic balance of the canine species in our breed populations. Moreover, the natural preponderance of heterozygotes is rendered even more important by overdominance effects, described below.

Genetic Drift

Small populations, such as most purebred dog breeds, are subject to a condition known as genetic drift. This is a situation in which gene frequencies change at random from generation to generation, varying from statistical expectations because of sampling error. (Sampling error occurs when too small a number of trials departs from the expectations of probability, as when someone flips a coin six times and gets five heads and one tail -- if he flipped it 600 times, the results would be close to 300 heads, 300 tails, but in a small sample, chance can cause a departure from the expected result.) This happens also when gametes unite to form zygotes in reproduction; the union of gametes is at random, by hazard. A dominant black dog, whose dam was white, when bred to a white bitch should in theory produce equal numbers of white and black pups, but few breeders would be very surprised to see 2 whites and 6 blacks, or vice versa. Yet when such sampling errors occur in small populations, over subsequent generations gene frequencies can change, taking a random walk that leads finally to the loss of one allele and the fixation of the other! The smaller the population, the fewer generations this result is likely to take. In a very large population, it will not happen at all. Genes are lost and other genes fixed completely at random in this way by genetic drift.

Generation Time

Since in limited, genetically isolated populations such as CKC breeds a certain amount of genetic diversity is lost with each reproductive event, through the action of genetic drift, inbreeding and artificial selection, the number of generations from the founder event becomes an issue. The average time between one generation and the next is a convenient yardstick to help us realise the relative rate of genetic attrition. A few instances exist in which certain bloodlines -- working dogs, usually -- are bred conservatively enough that the generation time is as much as an average six or seven years, but this appears to be exceptional. Many exhibition lines seem to operate on the following model: "Phoo-Phoo" starts his show career at six months of age in Junior Puppy class, is heavily "campaigned" and has all his Championship points by ten months of age. The owners' immediate "bragging ad" in "DOGS in Canada" or the breed club newsletter recounts his triumph, adding that "puppies from Ch. (subject to CKC confirmation) Phoo-Phoo are eagerly awaited next month!" In such lines the average generation time may be two years or even less. This reproductive rush has two implications: first, a greatly accelerated rate of loss of genetic diversity; second, an implicit selection for early maturity which carries with it an elevated risk of joint disease and a lowering of average longevity.

Effective Breeding Population

The population figure that matters in situations such as random genetic drift is not the total number of individuals alive at any one time. Nor is it even, as one might think, the actual number of individuals that contribute progeny to the next generation. Variations in breeding population from one generation to the next have a marked effect, such that the effective breeding population, especially where variations in number are extreme, tends to be only modestly greater than the lowest number. Another factor which makes a great difference and is crucially important in purebred animals is the sex ratio of successful reproductors. The effective breeding population can never be greater than four times the number of males, no matter how numerous the females may be, since gametes must come from both sexes. Thus anything that limits the number of males in use drastically restricts the effective breeding population. Overuse of popular sires is a tremendous factor in the genetic impoverishment of purebred dogs. One of the major drawbacks of the proposed CKC Advanced Registry is the virtual certainty that the existence and promotion of a few "elite" sires, titled, temperament-tested, and certified "clear" of major hereditary diseases, will further dramatically reduce the effective breeding population in many breeds, causing further declines in breed vitality and viability and leading to the loss of vitally-needed breeding lines which happen not to be among the elite group.

Linkage Disequilibrium

Genes found on the same chromosome will fail to assort independently in accordance with Mendelian principles. Such genes are said to be in a state of linkage disequilibrium. This simple fact has a devastating effect in artificial selection, since it means in practice that when a breeder selects for or against any single-gene trait whatever, whether he is aware of the fact or not he is also selecting for or against every other gene located on the same chromosome! This is how genetic defects become rapidly fixed in inbred populations subjected to artificial selection. Since dogs have only 78 chromosomes (diploid number) but many many thousands of genes, obviously linkage disequilibrium can be tremendously influential. Genes that are linked eventually become unlinked over time (except in certain special situations) through crossing over, a process whereby chromosome pairs exchange segments of their DNA structure during meiosis. The unlinking process, however, is slow and unpredictable; it offers little hope of remedying the linkage disequilibrium problem in a few generations and of course is no help at all where deleterious alleles have already become fixed.

Overdominance

Situations exist in which a heterozygote individual enjoys a survival advantage over both the recessive homozygote and the dominant homozygote of the same gene; this is called overdominance or heterozygote superiority. As yet not much seems to be known about this mechanism and proven examples of specific overdominant genes are rare. Nonetheless this mechanism may be one reason (apart from their usually recessive nature) why genetic defects are persistently found in genomes despite their apparent fitness disadvantage in the homozygous state.

While on this subject it is worth noting that population genetics offers mathematical models for various forms of selective breeding, including the selective elimination of individuals bearing homozygous recessive genes for harmful traits. These models demonstrate that the elimination from the breeding population of individuals homozygous for unwanted traits has only the smallest effect in changing the allele frequency! It has been calculated, for example, that to reduce the expression of the recessive albino gene in humans from one in ten thousand to one in one million, simply by prohibiting albino (i.e. homozygote) individuals from having children, would require nine hundred generations of such selective breeding to accomplish! This is one of several reasons why screening programmes, although perhaps profitable for the veterinary profession, are of questionable effectiveness, since they identify only affected (usually homozygous) individuals.

Heterosis

More commonly known as hybrid vigour, heterosis is a situation in which a cross of two or sometimes three highly-inbred bloodlines displays enhanced performance for some desired trait, as for example higher yield in corn. It works best in plant species capable of self-fertilisation, but has been amply demonstrated in domestic livestock species. It is worth noting that in practice many different inbred lines must be developed at the same time, that most of the inbred lines become so unfit that they must be discarded as they become non-viable, and that considerable random trial of different crosses must be done to establish which lines will actually yield the desired result. Although the seed-grower's methods are unsuited to purebred dogs, the overall principle is of interest, since it is thought that heterosis works because of the heterozygosity of the hybrid generation, probably through the action of both dominant and overdominant genes. Geneticists are now starting to realise that the balanced-heterozygote systems of many wild species involve a heterosis effect which gives them a high degree of fitness.

Inbreeding Depression

As genetic variability diminishes and homozygosity rises through inbreeding, a syndrome known as inbreeding depression sets in. It is characterised by a reduction in viability (survival of individual progeny), birth weight, fecundity (number of young) and fertility (reproductive success), among other things. Much of it is caused by the homozygous presence of rare, deleterious recessive alleles. Part of it may also be due to the relative absence of overdominant heterozygote combinations. As inbreeding depression becomes more severe, highly inbred lines tend to become extinct through the loss of ability to reproduce successfully and/or inability of the young to survive. It varies somewhat in intensity from species to species, due probably to variations in the number and nature of lethal, sublethal and subvital alleles involved. Some wild mammals which show almost no juvenile mortality when bred in captivity without inbreeding, exhibit 100 percent juvenile mortality when inbred! A survey of captive breeding records for 44 species (Ralls and Ballou, 1979, 1982) showed that juvenile mortality of inbred young was higher than that of noninbred young in 41 of the 44 species for which records were analysed.

Genetic Load

The difference between the fittest genotype of a population and the average fitness of that population is known as genetic load. (Muller, 1950) It is, of course, caused by the presence of lethal, sublethal and subvital alleles. The more such alleles found in a population, the greater the genetic load. Genetic load is sometimes measured by the number of lethal equivalents, and the severity of inbreeding depression can be quantified in this way. Humans in general normally carry in a heterozygous state from 5 to 8 lethal equivalents per person -- genes or combinations of genes any one of which, if homozygous, would cause the death of the organism. It should be emphasised that genetic load is present in every population, since never are all individuals maximally fit. The presence of lethal, sublethal and subvital genes is a normal state of affairs in all species. Homozygotes for such genes are usually so infrequent as to have little effect on species fitness. It is only when founder events and inbreeding occur that the gene frequency of deleterious alleles rises and genetic defects start to become a problem as the growing genetic load degrades the fitness of the inbred, limited population. Thus in the case of purebred dogs the problem does not inhere in the presence of "defect" genes, but in the registry and breeding practices of the purebred dog fancy!

Balanced Heterozygous Population Structure

In recent decades growing evidence from DNA studies of protein polymorphism conclusively disproved the "classical" view of species as being homozygous at most loci, with the phenotypes of all individuals of a species conforming to that of a type specimen. Population geneticists and evolutionary biologists now realise that typological concepts are useless in a natural world in which populations may best be described genetically not as individuals conforming to a type but as arrays of genetic variability. Some of the implications of the "balance view" are elucidated by one geneticist as follows:

Species that are diploid and cross-fertilised (this includes all mammals, Ed.)... characteristically carry large stores of genetic variability in a balanced state in their populations...

Genetic recombination naturally generates diverse genetic types from the large field of variability in the gene pool. In order to meet environmental challenges, natural selection in many such organisms tends to develop a system based on the higher fitness of heterozygotes. These are maintained under regimes of selection that exploit the advantages of heterozygosity for many alleles simultaneously. In these, the large amount of genetic variability is continually being recombined as balanced hybrid vigour is maximised...

The genetic system is not a fixed and frozen entity but is dynamic and variable...

By its very nature, this genetic system is inimical to the perpetuation of sameness. At each reproductive event an enormous field of genetic variability is produced. Most of the variability is held in sexual populations by a complex balancing selection based on the superiority of fitness of heterozygotes...

The biological conserver, short of putting the DNA into liquid nitrogen, cannot hope to freeze the characteristics of any natural population, be it a deme (local population, Ed.), a subspecies, or a species.

--Hampton L. Carson, The Genetics of the Founder Effect, 1983

Efforts at artificial selection and breeding which attempt to defy this system of balanced heterozygosity and variability will almost certainly fall foul of the kind of difficulties we are now encountering in purebred dog breeds. It is hopeless to attempt to freeze the genetic characteristics of small populations and even the attempt, which is doomed to eventual failure, is quite costly in terms of the loss of hardiness and viability. Artificially selected populations, too, can and should be maintained in a state of dynamic heterozygous balance. Thus the entire problem of genetic defects would be minimised.

Assortative Mating

Assortative mating is a method of selective breeding capable of creating homozygosity for desired traits without having as great an effect on overall homozygosity as does inbreeding. It consists of mating phenotypically similar individuals that are not closely related. This method of selective breeding would be capable of maintaining a reasonable range of breed type in a balanced-heterozygosity breed system with an open studbook.

Having now acquired a few of the more crucial concepts of population genetics, we are prepared to examine in a new light the nineteenth-century system of dog breeding and registration which we have inherited. As we prepare to enter the twenty-first century, perhaps we can conceive a renewed system which will serve our dogs and their breeders far better than the present one.

The Crux of the Problem

As we face the millennium, the one problem which most concerns the entire purebred dog fancy is genetic defects. Breeders used to worry about overshot/undershot bite and cryptorchidism. Not much else of a genetic nature was cause for concern; fanciers were a lot more worried about distemper, hepatitis and internal parasites. Breeding programmes concentrated on individuals' visions of canine excellence. Then in the 1960s the tip of the genetic iceberg emerged as concern grew about a joint disorder called hip dysplasia. A control programme involving the examination of hip x-rays by a skilled scrutineer and the maintenance of a registry of animals "cleared" of the defect was established at the Ontario Veterinary College at Guelph, Ontario. Now after three decades of the OVC programme it has been pretty well established that "clear" animals with several generations of "clear" ancestry can nonetheless produce dysplastic progeny (Chidiac-Storimans 1995)! Hence the OVC control programme would seem to be of questionable effectiveness. As the generations of closed-studbook breeding have advanced, a panoply of other inherited problems has emerged in purebred dog breeds. There is no need to list them here; the list would be on its way to obsolescence in a month or so; veterinary research continues to define more inherited disorders regularly. Many breeders now run four-way screening programmes; some may screen for even more problems. Many breeders' selection programmes for various kinds of canine excellence must now be at a standstill -- all the selection is going into the effort to produce stock "clear" for eyes, hips, elbows, blood disorders, endocrine dysfunction, etc. Yet thirty years of x-rays have not eliminated hip dysplasia -- it is now widespread in breeds in which it was not a problem thirty years ago.

In December 1994 "Time" magazine published a scathing indictment of the American Kennel Club and of purebred dogs and their breeders, targeting in a cover story the problem of genetic ills, suggesting that the best use of pedigree papers was for housebreaking the puppies and recommending that the public satisfy its desire for canine companionship with mongrels. Since then, most of us have known we have an untenable situation on our hands. Our reputation as breeders of purebreds is now in tatters; we are caricatured in the media as greedy, uncaring producers of degenerate animals. The CKC's main response to the situation was a Board policy statement that "reputable breeders will provide a detailed written guarantee of the present and future good health of the dog and will not hesitate to uphold their guarantees." The policy statement, far from helping the situation, only saddled breeders officially with a heavy responsibility without enacting measures which might assist them in living up to it.

It is time for us as dog breeders to stand up for ourselves and for our dogs, to reject the imputation that we ourselves are individually to blame for the problem of genetic defects, and to demand swift remedial action by the Club and, if necessary, Agriculture Canada. The crux of the problem is the closed studbook and with it, the ideal of breed purity, the worship of type, and the pre-eminence of the championship show as goal and arbiter of most breeding programmes. Armed with the concepts of population genetics, we can now examine the last century of nineteenth-century dog breeding, ascertain what has gone wrong, and establish ways and means to correct the situation.

Earlier we stated that the recognition of a breed by a registry was a crucial event in its history, more crucial than it need be. That is because the usual practice has been to open the registry to foundation stock for a limited period, to inspect and register a small population of foundation animals, and then to close the registry to new genetic inflow forever after, with the sole exception of animals of the same breed imported from other registries and derived from the same or closely-related foundation stock. In recent decades there has usually been no unique Canadian foundation stock except in the case of indigenous breeds; CKC merely accepts registered stock from other jurisdictions. (Actually the relationship of CKC foundation stock to that of other registries has never been clearly defined, so far as I know. CKC accepts registration papers of other studbooks which it considers to be "reliable." So long as the export pedigree shows three generations of registered, numbered ancestry; import stock seems to be eligible for CKC status without question. The criteria involved are clerical, not genetic.) Most of the breeds we are familiar with were founded from sixty to over one hundred years ago. In those days Canada's population was much smaller than it is now; the canine population was correspondingly smaller, too. Thus the number of dogs accepted during the open-registry periods was rather limited.

The canine species possesses tremendous genetic diversity as a whole. Like most species, that diversity includes a genetic load, a wide variety of more or less deleterious alleles, probably quite a few of them held in a state of heterozygote superiority, so that although natural selection tends to eliminate homozygote recessives when they segregate, the bad alleles themselves maintain a strong presence due to the selective advantage of the superior heterozygote. What happens when a founder event occurs? Then it is possible that bad alleles, uncommon in the canine population as a whole, may achieve a much higher frequency of occurrence owing to their presence in a small founder population -- especially since the foundation stock of a newly-recognised breed will already be considerably inbred from the breed development process. Inbreeding and selection together raise homozygosity levels dramatically through the wholesale elimination of alleles from the genome. Those alleles may be unwanted by the creators of a new breed; nevertheless their elimination raises the allele frequency of whatever remains.

An Example from One Breed

Thus the recognition of a breed creates a founder event when the registry is opened; a limited number of breed foundation animals are selected, often from a population which has already undergone considerable inbreeding and selection. Let us take for an example the Siberian Husky breed. Registered in 1939, the initial CKC population consisted of 47 animals, all belonging to or bred by one kennel! Of those 47, nine were foundation stock of the kennel whose dogs were registered. Two of those were males imported from Siberia -- littermate brothers! The other seven were mostly related to one another. (Two were seven-eighths Siberian and one-eighth Malamute.) The other thirty-eight were all progeny and grand-progeny of the founders. Of the nine foundation animals, two were not bred from at all. Two were mated -- once only -- to each other: one only of their progeny contributed to further breeding. Of the two Siberia import males, one brother was always bred to the same bitch, producing a large number of progeny of identical pedigree; the other brother was usually bred to daughters of the first brother. Today, Siberian Husky lines that trace directly back to the Canadian foundation stock owe 25% of their pedigree lines to the first brother, 15% to the second brother, and 27% to the first brother's invariable mate! Two-thirds of the genetic heritage of these modern Siberian Huskies derives from only three foundation animals! This is not an exceptional situation, it is a fair example of the early breeding history of CKC breeds.

In the case of the Siberian Husky, then, (which happens to be my breed, with whose early history I am reasonably well familiar), The Canadian Kennel Club opened a registry in 1939, inspected one kennel's dogs and admitted four dozen closely-related individuals to the registry, which was then closed permanently. No effort was made to ensure a broad foundation, nor a numerous one, nor a genetically diverse one.

Just how permanently the registry was closed I recently found out when I imported from Russia a dog bred to the Siberian Husky standard! The dog was born in the Ural Mountains well within the boundaries of Siberia, from parents of Chukotkan village origins; he had three generations of known ancestry (without registration numbers since there is no official "Siberian Husky" registry in Russia). I was immediately told that the Club "did not know what to do" about my application to register the dog, that the protocols used to register breed foundation animals in 1939 were no longer valid, and that my dog "should not be used for breeding because it would probably be a long process," in spite of the fact that the dog had a valid FCI Export Pedigree from the Czech Republic (through which he was exported). A year and a half later after repeated in camera discussions, the import was refused recognition by the Board and Registration Committee on grounds of inadequate information (no ancestral registration numbers). Repeated calls for Club inspection of the import and offers to submit the animal to DNA tests and progeny testing were ignored. The registry is closed -- even to new Siberia imports!

For the past fifty-six years, then, all Siberian Huskies bred in Canada have stemmed from the 1939 registrations, or from American imports, which mostly stem from the same dogs CKC registered, plus perhaps three additional animals. The original foundation animals were poorly utilised and subsequent generations were so closely inbred that the two Siberia import males plus one bitch are even today still statistically equivalent to grandparents of every single Siberian now registered!

Thus the original founder event in my breed plus the closed studbook has resulted in a state of forced inbreeding for Siberian Huskies. There is no such thing as an outcross mating in Siberians in any genetically meaningful sense. A sire can be found, perhaps, who may have no ancestors in common with a bitch for the last 5 or 6 generations -- if one knows all Siberian bloodlines well enough and doesn't mind going a few thousand miles to find him -- but he will not be an outcross, because all of his ancestors and all of the bitch's ancestors are the same animals, once the pedigree is taken back far enough. It would be difficult to calculate inbreeding coefficients for fifteen to thirty generations of ancestry; software to handle calculations of that nature doesn't seem to be generally available to breeders. (After all, a thirty-generation pedigree would contain over two billion names...)

Thirty generations of breeding all going back to ten dogs or fewer represents an impressive feat of sustained inbreeding! Predictably enough, Siberian Huskies, which eighty-five years ago were probably the toughest, hardiest variety of dogs on earth, now suffer from the same gamut of genetic defects that afflicts other breeds. Few if any registered Siberians are now able to perform as sleddogs on anything approaching the level of the 1910 dogs imported from Siberia. Probably this is mostly due to the decline in heterozygosity and loss of vitality through inbreeding. What is worse, unmistakable signs of inbreeding depression are surfacing in the breed: rising numbers of Caesarean births, smaller litters, lower birth weights, delicate nestlings prone to infection, etc.

Breeders of domestic livestock -- cattle, poultry, sheep -- manage to run registries and maintain breed type without imposing the concept of absolute breed purity. They inbreed to fix desirable traits, as do dog breeders. Livestock breeders, however, do not try to pretend that they can inbreed forever without ill effects. Thus when inbreeding depression or genetic defects threaten, they outcross -- repeatedly, if necessary. They can do so because they do not have closed studbooks. I do not suggest that we slavishly copy the procedures and registry structures of livestock associations, because I think they, too, might benefit from some restructuring in the light of modern genetic knowledge. Nonetheless I would make the point that we in the canine fancy are in a minority when we cling to absolute ideals of breed purity and insist on rigidly closed studbooks.

As a dramatic contrast to the foregoing example of the CKC's Siberian Husky breed foundation, let us examine for a moment the standards which Agriculture Canada now applies to new domestic animal breeds in this country, as set forth in a three-page leaflet entitled "Establishment of a New Breed of Animals in Canada." Agriculture Canada now requires that breed foundation stock (that is to say, the first generation of registered animals of a new breed) be selected from the third filial generation (F3) or later of the "evolving breed" which precedes the actual, registered new breed. It lays down no parameters for the founder generation of the evolving breed, but it does state:

The standard used for the creation of a new breed is as follows:

- Minimum number of animals to constitute the foundation stock of the new breed (F3): 200 animals (unique genotypes).

- In order to reach the required 200 F3 animals and in order to provide a sufficiently wide genetic base, it is recommended that the minimum number of animals to be produced in each F level be:
F1: 60 animals
F2: 100 animals

It also stipulates that "the F3 generation is the earliest generation to become eligible for inspection as foundation stock... In practice most evolving breeds will evolve over many generations before having developed a significant population of foundation animals."

These modern standards are at least somewhat influenced by population genetics considerations, in an attempt to establish a basis for genetic health and stability for new animal breeds in Canada. Yet in all probability very few of our existing CKC dog breeds, which are arguably of much greater economic importance than any new breed, would come anywhere near to the foundation stock numbers now enforced by Agriculture Canada. The sole exceptions would probably be breeds, like the Canadian Eskimo Dog, accepted for registration during the last decade or two. As for the Siberian Husky, its actual genetic founders (those whose genes contributed to future generations, leaving aside those which did not reproduce) numbered 6 only; the F1 generation which actually reproduced numbered 8 individuals; the F2 generation which actually reproduced numbered just 5 animals; no F3 animals were registered in the first year of CKC registrations -- original founders, F1s and F2s were all registered together in the first year.

Thus it is obvious that the Siberian Husky, at least, could not begin to satisfy current Agriculture Canada standards for an appropriate number and variety of foundation stock to establish a new breed, when traced to its historic foundation. In all probability, few CKC breeds could do so. Yet the registry norms that are rigidly enforced by CKC, backed up by Agriculture Canada, make the acceptance into the studbook of badly-needed new foundation stock a complete impossibility! Presumably Agriculture Canada has good and sufficient reasons justifying its standard for new breeds -- that being the case, then it is a curiously irrational situation that older, existing registered breeds not only are exempt from any such standard, but are actually prohibited from enlarging their founder group by the acceptance of unrelated primitive stock.

The Holistic Breed

Now I would like to evoke a vision of the future -- but not the distant future. I want to describe how dog breeds might be in the twenty-first century. Instead of all breeds being subjected to arbitrary structures not equally well-suited to them all, each breed would get whatever special measures its breeders thought necessary. Instead of a fragmented canine fancy with ghettos of show fanciers, obedience buffs, and working-dog specialists, dog breeds would have the benefit of a holistic outlook, integrating the various aspects of canine activity and producing well-rounded, versatile, mentally stable animals. Let me stress that the suggestions which follow will be fully practical and down-to-earth. They involve no technology we don't already possess. They require no knowledge that isn't already generally available. All that is needed is a proactive attitude and the will to make necessary changes in an obsolescent structure. This vision could become a reality within ten years' time.

At the beginning of this brief I stated that the three distinct axes along which breeds are distinguished -- ancestry, purpose, and typology -- had to relate fully and co-operatively, or the fulness of breed identity would be missing or marred. Let me now describe how such a relationship might be achieved.

To begin with, we absolutely must open CKC studbooks, in every breed, to new genetic inflow. There can be no long-term genetic health in small populations such as our registered breeds without the periodic infusion of new genetic material. The one big "sacrifice" we shall have to make, if it is really a sacrifice, is to abandon racist attitudes and the concept of rigorous breed purity. We must recognise that first of all, a dog is a dog, species Canis familiaris, and that is his true identity. He is a dog first, before he is a Siberian Husky or a Foxhound or a Doberman; breed identity is subordinate to species identity. We must stop treating breeds as if they were species, abandon the rigidity and narrow typological thinking which has heretofore characterised the canine fancy. We must recognise that dogs are unique individuals and that there is no positive value in trying to create groups of dogs which are all clones or photocopies of a type specimen represented by a breed standard. This should not be too hard, since breeders and judges have never been able to arrive at agreed and consistent interpretations of breed standards anyway. Why, then, should we pretend that a standard, which as it now exists evokes a different imagistic interpretation in the mind of each individual breeder and judge, describes a single ideal type?

Canine breeds can and should be differentiated, bred and maintained on a dynamically balanced, heterozygous population basis without restriction to a closed, historic founder group. The closed studbook and the breed purity concept are, from a genetic point of view, simply unnecessary. Indeed, as we have seen, from the standpoint of maintaining a genetically healthy limited population, they are thoroughly counterproductive. Where is the logic in submitting each and every CKC breed to a registry system which guarantees ongoing, progressive genetic degeneration, loss of species vigour and hardiness, and saddles every breeder with the unwanted, unhappy responsibility of producing more and more unhealthy, flawed stock as time goes by? The notion that genetic disease can be controlled, much less eliminated, by screening programmes and selection has not been borne out by general experience. Those who promote such a notion are engaging in a cruel, self-serving deception. It may be that a breeder can sometimes improve his odds against producing defective stock in a given mating by screening the parents, but experience has proved that screening will not solve our genetic problems in any wider sense. Despite generation after generation of "clear" stock, bloodlines can still produce more and more affected animals. That is because our problems are inherent in the closed studbook/incest breeding system. In order to restore genetic health we shall have to adopt a different system.

It will be asked, "Just how will the opening of our studbooks to outcross stock bring about the elimination of genetic defects?" The answer is that it will not eliminate genetic defects. That need not be the end in view. If we could somehow eliminate all the various genes now known to produce harmful anomalies, plus all of those yet to be discovered, we would almost certainly find that the remaining genome was non-viable, that healthy reproduction and growth to maturity could not reliably take place. Genetic defects are not "eliminated" in nature. Instead, random mating and behaviour patterns that discourage inbreeding take care of the problem by ensuring high levels of heterozygosity and the consequent rarity of defective homozygotes. If we take steps to set up similar patterns in purebred dogs, we shall be able to reduce the level of expression of defective genes greatly, which is all that is required. The end in view is healthy stock, not "racial purity." Purged and purified bloodlines would be weak for other reasons, as has been explained. As the mapping of the canine genome progresses and RFLP, allozyme or microsatellite "markers" for common genetic defects are found, we shall probably then be able to use DNA studies to recommend matings that will avoid the production of defective homozygote progeny -- provided that we have made enough genetic diversity available through outcrossing to give us the genetically distinct lines from which to choose! As things stand now, most breeds are so homozygous that it could prove extremely difficult to find matings which would avoid one genetic defect without reinforcing another!

New Structures for the Dog Fancy

Very well, then, if we eliminate the closed studbook, how shall we decide what stock to admit for registration? One must begin, of course, with the existing body of registered stock. Thereafter, one way of proceeding might be to strengthen and empower the breed clubs. They should be granted responsibility and autonomy: responsibility for the welfare of their breeds, and autonomy to make the judgments and decisions necessary to fulfil that responsibility. It should also be ensured that the breed clubs are fully representative of all breeders, by making breed club membership a requirement for anyone wishing to register stock he has bred or imported.

The first task of the breed clubs would then be for each of them to determine what sources of genetic inflow might best be employed in their breed. Breeders alone can command the collective expertise to make that decision and it ought to be theirs alone, but the designation of outcross sources should be obligatory, not optional. The Siberian Husky Club of Canada, for example, would have to decide where outcross animals might best be obtained for restoring heterozygosity to that breed; they might decide, for example, that dogs imported from Russia and perhaps even an occasional outstanding individual carefully selected from the present "alaskan husky" gene pool of racing sleddogs (which was derived largely from 1910-era Siberia imports that remained in Alaska) are two logical sources. Breeds which do not have their origins in autochthonous populations would have to seek outcrosses in similar related breeds, as Spaniels (English Springer) and Spaniels (Welsh Springer), or Retrievers (Labrador) and Retrievers (Flat-Coated). They would then have to set up inspection and test-breeding procedures for admitting outcross animals. Once the outcross sources had been designated, selection of candidate animals would in most cases be best left to individual breeders, who might then apply to the breed club for preliminary inspection of their outcross -- which inspection ought not to be excessively rigorous. General soundness, reasonable temperament, proven working ability, approximate size and physique, and acceptable overall type would be adequate criteria, none of the foregoing to be rigidly interpreted. The outcross should then be registered provisionally by CKC, subject to breed club inspection of two generations of its progeny. The registry should remain permanently open to new outcross animals. It might prove desirable to set limits to the number of outcross dogs registered in any given year, proportionate to the overall breed population, in order that small populations not be swamped by excessive outcrossing. Some regulation of the process would obviously be necessary, but the best regulation would probably be breed club oversight and guidance of the process, backed up by CKC supervision.

Advantage should be taken of DNA analysis techniques by using them to monitor heterozygosity and relative kinship in major breeding lines. (It would also be a good idea for the Club to offer DNA profile parentage certification.) This technology already exists and is in use; it is rapidly becoming much more affordable. Limits should definitely be set on inbreeding, preferably by the breed clubs, but CKC should decide maximum allowable limits of inbreeding as a default setting. Only by the outright prohibition of excessive degrees of inbreeding will it be possible to make the transition to a balanced-heterozygote state for purebreds; otherwise old ways will continue through inertia and persistent typological thinking. Assortative mating can and should become the norm for the preservation of type, mating individuals which are phenotypically similar but unrelated or at least not closely related. The Club would have to monitor registrations, possibly performing occasional DNA spot-checks, to ensure that inbreeding does not take place; otherwise many would continue to breed from whatever dogs were in their own backyard rather than seeking breed club advice to find suitable individuals from unrelated lineage.

A Healthy Balance for Breed Identity

The responsibilities of the breed club should not end with the designation of outcross sources and the inspection of outcross candidates. If the fulness of breed identity is to be achieved overall in each population, then the breed clubs should take on responsibility for balancing the various facets of that breed identity. Realistic, meaningful and workable systems should be introduced for monitoring temperament, for proving working ability and trainability, and for evaluating type and appearance. Championship shows would then become breed-club events, since the methods of evaluation and the various events required to test such qualities as temperament, vigour and endurance, working ability, and trainability would be breed-specific and under the breed clubs' oversight. That is not to say that a number of breed clubs might not band together to stage events for several breeds simultaneously at the same venue, but the all-breed show with all-rounder judges, under CKC rules for CKC Championship points, would eventually be history. To ensure wholehearted support and participation by breeders, it would probably be necessary for CKC to evolve some means of making clear on the papers of every dog the extent to which that animal had been submitted to the testing and evaluation procedures of the breed club and with what result. Breed club input of information to the Club's database could be done by e-mail on the day of the event. Strong incentives for participation should be arranged and breed clubs should be so structured that they could not be autocratically ruled by individuals or cliques.

Registration certificates produced by CKC would carry much more detailed information under the new system than they now do. The computer power is now available to make this quite feasible. A certificate of registration should once again carry a pedigree of at least four generations. A two-tier certificate system would be necessary, as no dog would be eligible for breeding registered progeny until it had been inspected and evaluated by the breed club. Rating and measurement protocols are already being worked out by proponents of the Advanced Registry proposal. Broodstock certificates should carry a summary of the breed club's rating and evaluation of the animal, together with evidence of proof tests for temperament, working ability and trainability. All certificates should identify outcross lines and bear a quantitative estimate of the relative heterozygosity of the animal identified by the certificate.

Breed standards would require revision under the new system. The concept of disqualifications should probably be dropped in favour of a detailed rating system in which all breeding stock would participate. In the case of quantitative characteristics such as height and weight, a simple Bell-curve statistical description of the desired mean and range ought to be sufficient, without disallowing occasional extreme examples. Working abilities ought to be clearly defined in the breed standard and a basic performance standard given where possible. Clearer and more detailed descriptions of desired temperament and of qualities bearing on trainability ought to be part of the new standards. Prescriptive minutia should be minimal; it should be sufficient merely to describe the general distinguishing features of a breed, without an excess of cosmetic and conformation restrictions, except where indispensable breed points are involved. Type stringencies should be relaxed considerably, allowing most breeds to become moderately heterotypic; if qualities of working ability, hunting instincts and similar traits achieve greater emphasis, there will be correspondingly less need for extreme type requirements to distinguish breeds. Standards should be holistic descriptions of the breeds they identify, brief statements of essential breed qualities, rather than typological blueprints. It is imperative to subordinate typological thinking to considerations of utility, genetic health and hardiness. First a dog should be healthy, balanced, of sound mind in a sound body, able to fulfil his breed purpose; after that can come points of beauty and type but never again in the bizarrely exaggerated fashion that now prevails in the breed rings of championship shows.

It might eventually be found desirable to quietly merge scarce and consistently unpopular breeds, as well as closely similar breeds, with populations nearest to them in general characteristics, possibly initially designating them as breed varieties. Reasonable numbers are necessary for the maintenance of a healthy population. The number of breeds recognised has continued to grow, yet the total number of dog owners in the country may not have grown proportionally. A rare breed is not the same thing as an endangered species; breeds can come and go without damage to the canine species as a whole. Breeds known to be of low viability due to their dependence for breed identity on anomalies such as achondroplasia, may have to be dropped from the registry unless evidence is advanced that they can be upgraded to certain minimum standards of health and structural soundness.

Can it Really Work?

I can hear someone objecting, after having thought about the idea of a breeding and registry system in which outcross breeding was actually encouraged, "Surely this system will produce some dogs which are not even recognisable representatives of their breeds! What happens then?" Typological thinking dies hard. I used to worry lest my Siberian breeding programme should one day produce a dog or dogs whose ears were not fully erect. It never happened. Instead something much worse happened when I found that I was producing some dogs who ran a high risk of being unable to lead a healthy, normal canine existence, through endocrine malfunctions, immune system weakness, and the risk of blindness. To think I had worried about the possibility of a tipped ear, something which would not handicap or bother the dog in the least! Let me say the following, then, to those who worry that a balanced-heterozygote breed will engender "untypical" examples. It is far better that our breeding occasionally engender a dog deficient in breed type, than that we should consistently produce large numbers of dogs guaranteed to lead lives of suffering, creating anxiety, large veterinary bills, frustration and unhappiness for their owners. That is what we are doing now. Over sixty percent of Golden Retrievers, for example, will suffer from hip dysplasia, osteoarthritis or osteochondritis in their lifetimes. Is that to be preferred to the possibility of producing an occasional robust "mutt" lacking in breed type but who will nonetheless still make someone an excellent, happy, healthy companion? I am sure that it would take awhile for all of us to learn how to breed in this new and different way; I suppose we might produce occasional oddities in the process. Yet I am absolutely convinced that the good results we would quickly achieve would more than make up for the embarrassment of our failures. At the very least we should all have clean consciences once again, knowing that we were making our best efforts, using up-to-date genetic knowledge, to produce sane, healthy, robust canine companions. Let us not forget that as DNA mapping procedures advance (there are at least two canine genome mapping projects now underway) our tools are going to improve and our ability to predict what our breedings may produce will be greatly enhanced.

As things now stand, the dog fancy is in a position which is frankly untenable. The CKC Board of Directors has unilaterally committed "reputable breeders" to the proposition of guaranteeing the "future genetic good health" of the dogs they sell. Yet those same breeders have no means of protecting themselves from the looming spectre of financial ruin should they be held to such a guarantee, otherwise to the loss of public credibility. Other than the continued elaboration of screening programmes and the Advanced Registry proposal, both of which are somewhat like applying an adhesive bandage to a severed artery, nothing is being done about making guarantees of genetic health a workable proposition. At present, purebred breeds -- all breeds -- show levels of genetic defects totally inconsistent with the practical maintenance of the Board's policy. Many honest, caring breeders are racked by torments of guilt and self-reproach brought on by the sufferings of defective dogs, yet it is really no fault of the breeders themselves! The fault, as has been demonstrated in this brief, lies with the closed studbook and the inbreeding system. If the consensus of the Club is truly that purchasers of purebred dogs have a right to expect genetically healthy animals, then the Board has no choice other than to do everything in its power to change the existing system so that healthy animals may once again be reliably produced! That will never happen just through Advanced Registries, higher Championship point requirements, more screening programmes, and Board policy pronouncements. The Club must take to heart the lessons of population genetics. It must open its studbooks to outcross stock on a permanent basis. It must take measures against the obsessive pursuit of breed type and the worship of breed purity, measures which will increase the health, utility, trainability and sanity of purebred dogs, measures which will balance the elements of breed identity. There are no credible "soft options" left.

One unfortunate reality which must be faced, however, in order to bring about any major changes involving the CKC will be the conservatism and resistance to change of the Board and of the "old hands" -- the ruling oligarchy of the Club. The CEO and the Board will almost certainly aggressively defend the status quo no matter how urgent the need for change. At present, for example, they turn down requests for the registration of new foundation animals with statements such as this one: "The CKC takes pride in registering dogs based on accurate and complete information and we will continue to strive for these high standards." Yet when that statement was written, the Club was still registering Canadian-bred litters whose parentage information was supported only by a signed registration application form filled out by the owners of the dam and sire. Under that system of information gathering it is regularly necessary for the Board to cancel litter registrations when it becomes evident that the parents of some litters are not both of the same breed. No one knows how many litters go unchallenged which, although purebred with both parents of the same breed, have their parentage misrepresented because the actual sire of the litter is not the dog entered on the application form. In the absence of DNA testing, how can the substitution of sires be detected?

Meanwhile the United Kennel Club, a "dissident registry" in Kalamazoo, MI, USA, which now registers about a quarter of a million dogs annually, has already instituted a process for the verification of parentage by DNA profiling! This is the first time that DNA profiling has been made routinely available to dog breeders, and UKC is the first canine registry in the world to offer such assurance of verified parentage. Innovations such as this make the Club's defensive statements about its high standards sound rather hollow.

Anyway, those of us who seek reform will have to contend with a Club establishment which will attempt to make a virtue of the very things which most threaten the genetic health of CKC dog breeds: the closed studbook, the breed purity concept, the endless inbreeding, the constant refinement of type, the pre-eminence of the Championship show, Those who dare to challenge the existing system will have to put up with being made to look foolish or even villainous by the solemn pronouncements of the old guard. We should all realise that the Club establishment is unlikely to initiate serious action for change in the absence of grass-roots pressure from the general membership. It is up to us to initiate serious dialogue along the lines outlined in this brief, to research ways and means to promote a different, healthier method of purebred dog breeding, and to raise the consciousness both of novices and of old hands regarding the genetic dilemma which now faces us.

Deep structural change cannot occur without widespread debate among fanciers, because new and different concepts sound threatening when they are first described. Once the reasoning behind them has been adequately discussed, the threat often disappears. Someone may ask, for example, "What about these open-ended Breed Standards? A Bell-curve statistical description of a breed's height standard may be an adequate formula, but what if the mean is set at 22.5 inches and you don't disqualify the 25-inch dogs. Then maybe in a few years the mean may drift upward to around 24 inches, with hardly a single dog under 22 inches. What then?" My answer would be that the whole point of the balanced-heterozygote system is its healthy flexibility. A stubborn insistence on narrow tolerances in matters such as height at withers usually involves the sacrifice of other worthwhile qualities anyway, as too many otherwise good animals must be discarded only because they are a shade over standard, In the balanced system described, nothing at all need be lost. If the height mean of a 22.5-inch breed should drift upward to 24 inches, it would be because most of the breeders wanted a taller dog! Since the breed club would be advising breeders, measuring and rating dogs, maybe even suggesting matings, this sort of gradual change would occur only with the knowledge and acquiescence of the breed club, representing all active breeders. Under a heterozygous plan with mainly assortative matings, nothing whatever is lost in such a gradual change. Should the height drift upwards and, later on, the breeders decide upon a return to the original mean, a simple shift in the emphasis of assortative mating will accomplish such a return easily, smoothly, with no genetic loss and no disturbance of other traits.

The whole idea of a dynamically balanced heterozygous breeding system is the retention of as much healthy genetic diversity as possible. Such diversity makes it easy for a breed to develop and progress in whatever direction its breeders wish. It also ensures that genetic problems are kept to a minimum no matter what changes of standard may occur. In the statically balanced homozygous system now in force, the more homozygosity increases with time and selective breeding, the harder it becomes for major change to occur naturally and easily, and the more pronounced genetic problems become. Once an allele has been "fixed" in homozygosity, no amount of selection can change that trait; only radical outcrossing can restore the lost alleles and such outcrosses will always upset the static balance completely, necessitating years of remedial inbreeding and selection, probably creating new genetic problems. I am convinced that a system based on a dynamic equilibrium of healthy dominant genes must inevitably be better than one which throws away most of the healthy genetic diversity in order to achieve static stability for homozygous recessive traits.

It is worth noting that the new system, if carried out at all conscientiously, would mean more work per dog for everyone. Breeders would necessarily invest more time and effort in their breeding stock in order for it to pass breed club requirements. This is by no means a negative factor. One ongoing problem in our society is that of large numbers of unwanted pets. Another related problem for the purebred fancy is substandard dogs produced by the non-serious "backyard" breeder and the puppy-mill profiteer. The suggested reform measures would discourage exploitative factions and reduce considerably the overall number of purebred dogs, while raising greatly the overall quality levels and ensuring that practically all purebred dogs were valuable, cherished, and wanted by their breeders and owners. The new system would greatly increase the inherent value of purebred canine stock. Purebred would then mean much more than just a paper certificate!

A Canine Revolution?

The foregoing prescriptions may sound like a canine revolution. If so, the revolution would consist mainly of integrating many facets of the fancy which now exist in ghetto isolation, or of importing good ideas from other parts of the cynological world. In Europe, for example, many breed clubs have long held responsibilities for their breeds similar to those described above. The only really revolutionary features of this new vision of purebred dogdom are the permanently open studbook and the abandonment of incest breeding, and those represent simple, inevitable acquiescence to genetic reality. If there is one thing we can do which will be of lasting benefit to the dogs we breed, it is to endow each and every one with a healthy, heterozygous genetic outfit. If that is to become possible, the closed studbook must go and inbreeding must go. There are no effective alternatives.

These reforms would require considerable co-operative effort on the part of breeders, breed clubs and the CKC in order to bring them into being. A major part of the job would be to convince Agriculture Canada of the desirability and feasibility of these proposals, followed by amendment of the Animal Pedigree Act to facilitate them. Yet when we consider the threat to the very existence of purebred dogs posed by genetic disease, the economic loss caused by genetic defects, and their widespread unhappy effect on people's lives, can we deny that radical and decisive remedial action is required? The goals of a balanced-heterozygote breeding system producing healthy, hardy dogs and a balanced breed identity structure coordinating all the delightful activities of purebred dogdom, would be worth any amount of effort. Let us begin work now to bring those goals into existence! Future generations of breeders and fanciers will be grateful to us for so doing and what is more, we shall be doing the best and kindest thing for our very best friends -- our dogs.

Postscript

Inevitably some will feel that the suggestions contained in this brief are unrealistic and impracticable, that ideas such as breed autonomy and balanced-heterozygote breeding "will never fly" in Canada. It may be that this brief is slightly ahead of its time; nevertheless, we are about to embark upon a new millennium. Already this country has seen the acceptance and adoption of many concepts that would never have been practicable fifty years ago. The Charter of Rights, settlement of aboriginal land claims, the Internet, the Quebec referendum -- none of these current realities would have been acceptable or seriously foreseeable in the first half of the twentieth century.

Many breeders will reject outright the mere idea of deliberately trying to increase heterozygosity, after so many years in the pursuit of homozygosity through "linebreeding" and frank incest breeding. Others will be horrified by the thought of dismantling the apparatus of the CKC Championship Show. Almost everyone, myself included, will be nervous and dubious about increasing the power and autonomy of breed clubs, based on the past performance of many such clubs. Yet needs must when the devil drives! The genetic situation is dire and the present outlook for many breeds is grave. Something will have to be done. Just now most of the hope and effort rests upon research towards detection of DNA markers for major genetic diseases. Yet those who promote this approach to the problem of genetic defects invariably seem to have a very narrow outlook, treating each defect in isolation. The approach is no different from that of traditional hip x-rays and eye examinations, except that it may be more efficient. The proponents of disease marker detection do not, however, explain how we are going to deal with the problem of diseases which are already widespread throughout a breed's population, or how our gene pools will stand up to successive waves of severe culling as we strive to "eliminate" one widespread genetic disease after another in our small populations bred from tiny founder groups. The population genetics aspect of marker detection, screening and subsequent selection is simply being ignored. As we have already found to our sorrow, those aspects of breeding and genetics which we ignore as being inconvenient at the time emerge later to work us woe.

Now is the time when we must begin a full and open dialogue among ourselves on the topics that have been mentioned in this brief. Now -- before we embark upon a devastating new wave of genetic attrition which could be the "killer wave" that sinks the ship of purebred dogs.

If the more advanced reforms suggested in this brief prove too unpopular for implementation, then so be it. What cannot be done now we may perhaps achieve in time. But at the very least, an irreducible minimum of reform must take place soon if we are to have any hope for the future of our dogs. The most critical item is relaxation of the closed studbook to allow for admission of new foundation stock. We cannot go on selecting rigidly forever and a day from a closed foundation, particularly not if we are to embark upon an era of new selection criteria based on marker research. A breed's gene pool may be likened to a bank account: one cannot go on making withdrawals forever without an occasional deposit (no matter what deficit-spending politicians may think). That some breeders are dead set against outcrossing does not imply that the rest of us should be prevented from introducing new genetic material if we feel it is needed in our own bloodlines. Likewise I think that the restoration of balanced breed identity is also a high priority item, which many people in the fancy are already well-prepared to welcome. Fanciers' interest, for example, in useful working dogs instead of mere beauty contestants has never been higher than it now appears to be.

It must also be pointed out that it would be extremely unwise for the CKC to ignore the need for genetic renewal. The Club's adoption of a hard-line position would carry a high risk of major schism within the ranks of purebred dog breeders. Already independent breed associations and alternative registries exist, promoting genetic excellence and asserting the need to "protect their breed from the kennel clubs"! CKC terms these organisations "dissident registries" although the associations themselves seem to feel it is questionable who is more dissident in view of the hostile position CKC adopts towards their pedigrees and stud books! In any case, the absence of a proactive, co-operative and open-minded response from the Club to the genetic crisis will almost guarantee the creation of alternative associations and stud books, dedicated to the pursuit of genetic excellence on a more practical basis than that offered by CKC. This author, for instance, fears that in order to incorporate new Siberia import stock into his bloodline of working sleddogs he may ultimately be obliged to adopt an "evolving breed" scenario under an independent association. Schism of this kind is perhaps in no one's best interests, but may be unavoidable should the CKC prove intransigent in refusing to re-open stud books to new foundation, as it has done to date. If more "dissident registries" should in fact arise and succeed in producing canine stock to a higher standard of genetic excellence than can be done within CKC, it would greatly damage the Club's credibility in the public eye.

What is of paramount importance is that we all recognise the true dimensions and gravity of the problems we now face. It is far too easy to ignore genetic diseases, to make excuses, to pay the vet bills and say nothing for fear that others will accuse one of breeding defective stock -- I think practically all of us live in fear of the smear tactics that are so common in the dog world. Yet the truth is that we are all breeding defective stock; the system itself virtually guarantees that. If we believe that to breed defective stock is a bad thing, then we simply must discuss ways and means of altering that system to allow us to restore genetic health. Too many breeders are now reluctantly deciding that "health must be the paramount concern" and abandoning their usual selection criteria in favour of breeding for hips, eyes, blood, etc. A few decades of that sort of breeding will surely do greater harm to breed characteristics than could ever be done by outcrossing. We must now seek to evolve a system which will naturally, almost automatically, produce healthy animals -- so that we may continue on with, or return to, our selection for temperament, working ability, conformation and breed type. Most of all, it is imperative that we start now to discuss and work on the new structures that are needed to facilitate genetic health for our dogs. The next millennium, close as it is, may be too late.

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Glossary

In the hope of helping the reader to understand certain genetic and other terms which may be unfamiliar, I have included this Glossary. It does not explain terms or concepts that have already been explained elsewhere in the brief, as for example, the concepts treated in the section headed "Lessons From Population Genetics." I have included here mostly terms which are technical enough to be omitted from most dictionaries. If the reader finds other unfamiliar words in the brief, their definitions will be found in any good collegiate dictionary.

achondroplasia - a genetic syndrome producing skeletal development resulting in a semi-dwarf phenotype with shortened and distorted limbs; occurring in some breeds (Alaskan Malamutes, e.g.) as a genetic defect, it is selected for as a breed point in others (Basset Hound, e.g.).

allele - an alternative form of a given gene producing a difference in the trait controlled by that gene; some genes have no alleles, some have two, some have multiple alleles for the same trait.

allozyme - enzymes differing in electrophoretic mobility (i.e., which migrate different distances through the substrate when an electrophoresis test is performed) as a result of allelic differences in a single gene; allozyme variation thus indicates genetic variation. One of the oldest lab tests for genetic analysis.

autochthonous - "sprung from the earth," native to a particular region from a very early time. The Siberian sleddog is an autochthonous dog in Siberia. (Pronounced "aw-TOC-thun-us.")

chromosomes - structures within the nuclei of living cells which are made up of nucleotide sequences, the biochemical information carriers which we call genes. All genes exist as tiny portions of chromosomes; although we may speak of particular genes individually, in isolation, they do not exist as separate entities, but are always found as subunits of chromosomes.

cynological - of or pertaining to the knowledge and study of dogs.

deleterious - harmful or injurious.

diploid - the body cells of most complex animal organisms such as birds and mammals all have their chromosomes in pairs derived from sexual reproduction, such that one chromosome of a pair comes from the father, the other from the mother. The sex cells from only one parent have only half the number of chromosomes of cells in other parts of the body; the normal chromosome number is known as the diploid number, the chromosome number of sperm and egg cells is called the haploid number.

disequilibrium - imbalance or instability.

dominant - said of an allele which by itself alone will produce a particular phenotype regardless of which other allele may be present on the other matching chromosome of the diploid pair; thus it takes only one copy of the chromosome to cause a dominant trait to be expressed in the phenotype.

electrophoresis - one of the most useful lab techniques for revealing genetic variation, which came into widespread use in the 1960s. It involves placing sample material (blood, e.g.) on a gel substrate. An electrical field is then applied between the two ends of the substrate, causing protein molecules to migrate through the gel. Proteins with different ionic charge will travel different distances across the substrate. Staining subsequently makes bands of protein in the substrate visible, so that various samples can be "read" in much the same manner as a supermarket bar coded label.

expression - not all genes possessed by an organism will result in detectable physical traits or differences in that organism; the genes that do are expressed. Dominant genes are always expressed, but recessive genes may be present for many generations without physical expression in the phenotype.

fecundity - the number of progeny produced by animals when reproducing.

fertility - the relative degree of reproductive success, i.e. the frequency with which mating is followed by pregnancy.

gametes - the sex cells of sexually reproducing organisms, i.e. spermatozoa and ova.

genome - the total genetic information possessed by an individual, a breed or a species.

genotype - the invisible genetic makeup of an individual organism, which includes alleles which may be recessive and therefore have no visible physical expression.

heterotypic - displaying different types. A breed which has more than one distinct and recognisable set of "type" characteristics is heterotypic.

heterozygote - an organism that possesses different alleles at a given gene locus.

heterozygous - possessing different alleles at a given gene locus.

holistic - relating to or focussing on the entirety of a thing or an organism and the interrelationship of its component parts, instead of emphasising different aspects or parts in isolation without considering their interactions.

homozygote - an organism that possesses identical alleles at a given gene locus.

homozygous - possessing identical alleles at a given gene locus.

inbreeding coefficient - a number used to quantify the probability that an organism will have identical alleles from the same ancestral source, usually computed by analysing the pedigree for "loops" in which the same ancestor is found on both the male and female sides of a mating.

lethal - likely to cause or capable of causing the death of an organism. A lethal gene is one which could either cause an aborted fetus or the death of the organism at some later stage of its life.

locus (pl. loci) - the physical location of a given gene on a particular chromosome.

meiosis - the kind of cell division which produces spermatozoa and ova or gametes and which reduces the chromosome number to half the normal complement.

microsatellite - a kind of DNA testing which detects short DNA sequence variations at particular highly variable sites; used in so-called "DNA fingerprinting."

phenotype - the visible physical expression of an individual organism's invisible genetic makeup.

polymorphism - difference or variation in form, diversity. Molecular geneticists study protein polymorphism, different forms of proteins in an organism indicating different alleles. Polymorphism studies show that from 20 to 50 percent of gene loci in most species have two or more allele forms.

recessive - a gene which contributes to the phenotype only if it is present in homozygous form. It takes two identical copies of a recessive gene to produce the trait it governs in the phenotype. In practice many genes are neither clearly dominant nor recessive, in which case geneticists speak of variable expressivity or incomplete penetrance.

RFLP - "restriction fragment length polymorphism" -- a DNA analysis technique which involves the use of enzymes to break the DNA chain at specific nucleotide sequences; the resulting "restriction fragments" are then analysed by the use of electrophoresis and blotting techniques. RFLPs are used as markers for known genetic traits and can be employed for genome mapping.

sublethal - having known deleterious effects which by themselves will not usually cause the death of the organism but which handicap it in some way. Several sublethal genes may nevertheless combine to form a "lethal equivalent."

subvital - having known effects which work to reduce the overall vitality and health of the organism.

typology - the study of types or groups of distinguishing characteristics. Typological thinking involves emphasis on visible superficial characteristics, often mere cosmetic traits which have little to do with the health and viability of the animal possessing them.

viability - the relative survivorship of the fertilised ova resulting from a reproductive event. Non-viability may involve ova which simply fail to develop, fetuses which abort, nestlings which die, or juveniles which fail to survive to maturity.

Afterword

The author most sincerely hopes that the foregoing brief has in one way or another stimulated or inspired your thinking about the breeding and selection of purebred dogs into the twenty-first century. Our fancy badly needs a responsible long-term perspective, both for our own good as breeders and for the good of our animals.

If you should wish to comment on this brief, or if you should have some urgent unanswered question, the author will be happy to receive your letter at the address given below.

Should you feel indignant or upset after reading this brief, please put it aside for a few days, then read it again. I have introduced some ideas which, although they are becoming commonplace in other parts of the dog world, have largely failed as yet to reach Canada. Those who have accepted the gospel of breed purity, inbreeding, and type above all, as published in a multitude of magazine articles and "how to breed" books, may well feel betrayed or insulted! It is not my wish to insult or to upset anyone, but I have nothing against disturbing complacency. We shall all have to rise above our own narrow individual interests and perspectives if we are to save our purebred dog world from genetic disaster.

If this brief -- as I hope it will -- leaves you feeling that The Canadian Kennel Club should be approaching the matter of genetic health in purebreds in a different way, or should be considering new ideas, I hope that you will make your feelings clearly known to the Board of Directors by writing to the CKC Director for your region, whose name and address will be found on Page 2 of the "CKC Official Section" which is mailed every month to CKC members along with their copy of "DOGS in Canada."

In closing, I wish the best to all of us as we carry our breeding programmes forward into the twenty-first century.