Ectodermal dysplasia in German Shepherds

The mutation is X-linked. This means that it is localized on the X chromosome. Males have an X and a Y chromosome, so they can only be healthy (Xn/Y) or affected (Xm/Y). Females have two X chromosomes, so they can either be healthy (Xn/Xn), carriers (Xn/Xm) or affected (Xm/Xm). Female carriers do not show clinical signs but are able to pass the mutant allele to their offspring. Breeding of carrier females is not recommended. The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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Reference:

Casal, ML., Scheidt, JL., Rhodes, JL., Henthorn, PS., Werner, P. : Mutation identification in a canine model of X-linked ectodermal dysplasia. Mamm Genome 16:524-31, 2005. Pubmed reference: 16151697.