The coat colours black, chocolate/brown and cinnamon/red are controlled by the gene TYRP1 (tyrosinase-related protein 1) which is involved in the production of the black colour pigment eumelanin. This gene locus is also called the B-locus. The Coat Colour Cinnamon (K755) and Coat Colour Chocolate (K756) combined reveal the genetic status of the B-locus. The B-locus has three variants (alleles). The B allele is dominant over the alleles b and b’; allele b is dominant over allele b’. The dominant allele B results in a black coat colour. The allele b in a chocolate/brown colour and the allele b’ results in a cinnamon/red coat colour.
The Coat Colour Cinnamon and Coat Colour Chocolate tests (together B-locus) enclose the following results:
| Chocolate | Cinnamon | B-locus | Coat Colour |
|---|---|---|---|
| N/N | N/N | B/B | Black |
| N/N | N/b’ | B/b’ | Black |
| N/N | b’/b’ | b’/b’ | Cinnamon/Red |
| N/b | N/N | B/b | Black |
| N/b | N/b’ | b/b’ | Brown/chocolate |
| b/b | N/N | b/b | Brown/chocolate |