If XXSR in Kerries is an autosomal recessive trait, why are there no affected males?
Actually, there are “affected” males, in the sense that they have both defective copies of the gene (i.e., they are homozygous for the defective allele). They don’t show any abnormalities, though, since they have the SRY gene on their Y chromosome. Thus, the genetic program for male development is running anyway and the fact that one of the genes in the pathway isactivated in a different fashion is irrelevant. The danger of this situation is that all offspring of such an affected male will get a copy of the defective gene. If mated with a normal female, all offspring will be carriers. If mated with a carrier female, 50% of the offspring will be carriers and 50% will be affected (25% affected females and 25% homozygous males). If this affected dog was a popular stud, you can imagine how quickly the trait could spread throughout the breed!
