K-Locus (dominant black)
The K-Locus is a region of your dog's DNA which controls whether your dog has a solid coat colour.
The K-Locus has three alleles with an order of dominance:
KB > KBr > ky
This means that dominant black (KB) is dominant over brindle (KBr) which is dominant over yellow (ky).
In the vast majority of dog breeds, a dog will need to have at least one of the E or Em allele and at least one KB allele to have a solid coat colour (black, brown, or dilute).
If your dog has at least one copy of KB, known as dominant black, then their coat colour will be black, brown, or dilute. If your dog has two copies of the ky allele then their coat colour will be determined by the A-Locus.
The brindle allele doesn't have a DNA test as scientists haven't yet discovered the exact DNA mutation that causes a brindle coat. Brindle occurs all over the coat in dogs with an ay allele on the A-Locus but only the ventral (stomach) surface in dogs with at/at at the A-Locus. As KB is dominant, all visually brindle dogs must be KBr/KBr, or KBr/ky.
For a dog to have a solid coat colour it must be KB/KB or KB/ky on the K-Locus. For any A-Locus colouring to be visible it must be ky/ky at the K-Locus and E/E or E/e at the E-Locus.
The dominant black is caused by mutations in the DEFB103 gene with a dominance order as outlined above.
Results:
Your results will be reported as one combination of the K-locus alleles with the following interpretations.
| KB/KB | - two copies of dominant black (could be double brindle KBr/KBr, or a brindle carrier KB/KBr) |
| KB/ky | - one copy of dominant black (could be a brindle KBr/ky) |
| ky/ky | - no copies of dominant black (allows expression of the A-Locus) |
Scientific References: