World of Cats & DogsSex-Linked Disorders
For sex-linked (also known as x-linked) recessive defective genes for which carrier tests exist, breeders should follow the same “breed and replace” recommendations as are outlined above in the discussion of autosomal recessive disorders. If there is no test, the defective gene can be traced through the pedigree. Selecting a normal male for breeding loses the defective gene in one generation, regardless of his relationship to affected and carrier relatives. Carrier, affected, or high risk females should not be used, due to the high risk of producing affected male offspring. If a male is affected, he would have received the defective gene from his carrier mother. All of his daughters will be carriers, but none of his sons. Without a test for carriers, you can use relative-risk assessment to breed him to a female that is at low risk of being a carrier. This minimizes the chance of producing affected offspring, and a quality son can be selected for replacement. Rare sex-linked dominant disorders are managed the same way as autosomal dominant disorders. The difference is that affected males will always produce all affected daughters.