To Breed or not to Breed? That Is the Question. Pre-breeding and Genetic Evaluation

The recent sequencing of the canine genome has opened up a whole new frontier in veterinary medicine. In the last century, veterinary medicine has made major advances in treating and eliminating many diseases through vaccination, parasite control and proper nutrition. A whole new realm of possibilities for diagnosis, prevention and treatment of disease is on the horizon with genetic modalities. Over 200 genes and their function have been identified in the canine genome—genes specific for phenotype (such as coat color and hair pattern) or breed-specific diseases (such as retinal atrophy, and von Willebrand’s disease).

The genetic disease often results from a single mutation in an individual’s DNA. The mutation may be a point mutation, translocation, repeat or insertion affecting a gene or its promoter. Subsequently, the gene’s encoded protein is malformed or eliminated; altering its activity, transport function, or receptor function. If these genetic changes result in favorable characteristic changes, we preferentially select for them. If the mutations results in unfavorable characteristic changes, we call it disease. Mammals are diploid and carry two genes for each function. The corresponding gene on the alternate chromosome may produce the normal protein and completely or partially compensate for the mutation’s effect. This is known as a recessive trait mutation. In the homozygous state, both genes are affected and the mutation will be expressed. If the mutation alters a dominant gene, the effect will be expressed even if only a single gene is mutated. When disease occurs from a dominant trait mutation, it is readily identified and eliminated through selective breeding.  [...]