Coat colour K locus / Dominant black (CBD103-related) - Dog

What does this test examine?

This genetic test analyses the CBD103 variant c.231_233del at the canine K locus. The trait is known as K locus, dominant black, Dominant Black, K^B and beta-defensin 103-related black coat colour.

What does the K locus mean for the coat?

CBD103 influences pigment switching through interaction with MC1R. A dog with at least one K^B allele produces mainly dark pigment in many coat areas, so A-locus patterns such as sable, agouti or tan points are often masked. The visible base colour still depends on E locus, B locus, D locus, white spotting and other modifiers.

Inheritance and result

The K^B allele acts as autosomal dominant. A dog with K^y/K^y does not carry the tested dominant black deletion, K^B/K^y carries one copy and K^B/K^B carries two copies. Brindle is classically placed as k^br within the K-locus hierarchy, but this test focuses on the known CBD103 K^B deletion.

Practical value of this test

• Helps breeders determine whether A-locus patterns can be visible or are masked by dominant black.
• Makes hidden colour information easier to interpret in black, brown, blue or dilute dogs.
• Supports targeted colour planning and puppy expectations together with A, E, B, D and S locus results.
• Gives buyers and owners a clear explanation of why a dog can carry patterns that are not visible in the coat.