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