The genetic test is intended to show whether a double or single hair coat is present. However, the results must be critically scrutinised and other factors probably also play a role.
A dog's coat varies not only in the length and structure of individual hairs but also in whether it is a double coat (double layer) or single coat (single layer). Wolves, with their distinctive double coats consisting of two layers, are perfectly adapted to the environmental conditions of their habitat. This characteristic is also found primarily in working dog breeds such as sheepdogs and some hunting dog breeds.
Single coats are common in many short-haired breeds that are kept indoors or as family pets, such as watchdogs and various terrier breeds.
The two types of coats differ in function and hair structure. While all dogs have a primary or top coat that forms a protective top layer and contributes to the dog's color, the numerous fine hairs of the undercoat, found only in double-coated dogs, are very soft and serve as insulation.
Two genetic variants have been identified that correlate with double and single coats. The allele 'A' (ancestral), considered a wild-type variant, is found in both wolves and most dogs with double coats, while the recessive allele 'D' (derived) is predominantly found in homozygous form in dogs with single coats.
Genetic testing for these variants can be used in breeding programs to select dogs with the desired coat type and corresponding genotype. This is particularly important in double-coated breeds, where a single coat and the associated lack of an undercoat are considered faults according to the breed standard.
Preliminary statistics on the distribution of these variants suggest that other genetic factors may also play a role, as not all phenotypes correlate directly with the genotypes determined so far using the double coat test.
