World of Cats & Dogs

Autosomal Dominant Disorders

Autosomal dominant genetic disorders are usually easy to manage. Each affected animal has at least one affected parent, but it can be expected that half of the offspring of an affected animal will be free of the defective gene. With disorders that cause death or discomfort, the recommendation is to not breed affected animals. To produce the next generation of a line; a normal full sibling of an affected animal, a normal close relative, or the parent that is normal can be used.

If the defective gene is at a high frequency in the gene pool, eliminating all affected breeding animals in one generation may have a significant negative impact on genetic diversity. When a high frequency autosomal dominant disorder is first identified, some quality, affected animals may have to be bred, and replaced with quality, normal testing offspring. However, once a few generations have gone by and breeders have had the opportunity to replace affected with normal individuals, the continued breeding of affected animals is not ethical.

A problem with some autosomal dominant disorders is incomplete penetrance; where some animals with the defective gene may not show the disorder. Roughly half their offspring, however, may be affected. If a genetic test is available, this is not a problem. Otherwise, pedigree analysis and relative-risk assessment can identify which animals are at risk of carrying incompletely penetrant dominant genes.