Dog Inheritance Control
George A. Pagett, an outstanding veterinarian and geneticist, suggested that breeders, as an urgent and priority task, set priorities in the fight against hereditary diseases. He meant that the higher the mortality and severity of the disease, the more intensively the selection against him should be conducted. The intensity of selection should also be determined by the frequency of the defective gene (s) in the population. Of course, the success of the fight depends on the availability of genetic diagnostic methods. Recently, dog breeders have at their disposal another sign for selecting pairs or choosing producers – this is the presence of a dog’s certificate of passed genetic tests. Breeders were and remain custodians of breeds. And the well-being of the breeds, and sometimes the continuation of their existence, largely depends on how they can manage the information that the tests provide them. “First of all, do no harm” – the first commandment of medicine, which remains central in this case. Genetic tests are a powerful tool, and their use can lead to significant, both positive and negative changes in the gene pool of the breed. That is why George Pagett spent more than one year of his life collecting data on the manifestation of hereditary diseases in dogs and test results for all breeds, for this he wrote his book, which appeared in Russia after the death of the author.
Lecture by Gerald Bell
“On the practical aspects of the control of genetic diseases of dogs for dog handlers and breeders”
Moscow State Veterinary Academy named after Scriabin, Moscow, 2006
Gerald Bell is a doctor of veterinary medicine, professor of the Department of Clinical Research at Tufts University, USA.
The lecture by J. Bell was organized by Sophion Publishing House and timed to coincide with the publication of the Russian edition of George A. Padgett’s “Control of Canine Genetic Disease” book.
Everything is in the genes
As dog breeders, we do genetic “experiments” whenever we plan to mate. The type of matching knit combination should match your goals. For some breeders, the problem of determining which traits will appear in the offspring is like playing a dice – lucky – no luck. For others, getting certain traits from offspring is a matter of more art than luck, that is, the result of careful research and planning. As breeders, we need to understand how we manage genes within our breeding stock to produce the type of dogs we want. We must first understand dogs as a species, then dogs as genetic individuals.
Species Canis familiaris, i.e. common dog, includes all breeds of domestic dogs. Although we can argue that the Chihuahua and St. Bernard have very little in common, or that the recognized breeds themselves are independent entities, genetically they are all representatives of the same species. While mating within the breed can be considered unrelated, it should still be considered as part of the whole genetic picture: mating within an isolated, closely related population. Each breed was bred by closely related breeding and inbreeding among a small group of canine ancestors, either during a long genetic selection, or by intensive inbreeding for fewer generations. During this process, breed characteristics were established and the breed type was fixed.
When evaluating a breeding program, it must be remembered that most of the traits you strive for cannot be changed, fixed or created in one generation (generation). The more information you can get about how certain traits were conveyed by your dog’s ancestors, the better you can prioritize your breeding goals. Tens of thousands of genes interact to produce each specific dog. All genes are inherited in pairs, one in pairs from the father and one from the mother. If in a pair the genes inherited from both parents are identical, the pair is called homozygous. If the genes in a pair are not identical, the pair is called heterozygous. Fortunately, the pair of genes that make a dog a dog, not a cat, is always homozygous. Similarly, the pairs of genes that are responsible for the breed type are also homozygous. Therefore, in each breed there is a large proportion of homozygous non-changing pairs, those that give the breed its characteristic standard. And there are variable gene pairs, similar to those that are responsible for color, size and proportions, which serve as the cause of variations within the breed.
In outbreeding (unrelated mating) we cross two dogs with a lower degree of kinship, average for the breed. This contributes to greater heterozygosity and gene diversity by combining pairs of unrelated genes from different ancestors. Outbreeding can also hide the manifestation of recessive genes and allow their distribution in a state of carriage.