Cat Coat Color – B locus (Brown)
B locus can contain alleles responsible for brown coat colors in cats. Brown coat color phenotypes have been recognized in the domestic cat for over 100 years. The cat locus for the brown phenotypes was originally designated as Brown, B. The wild-type black (B) allele is dominant with normal, black (eumelanin) coloration. Cats with a brown (b) allele, either bb or bbl genotypes, are chocolate (aka chestnut), and the phenotype resulting from light brown homozygotes, blbl, are cinnamon (aka red). In order for cat to have expressed brown coat color phenotypes, it must be homozygous, and not containing the wild-type black (B) allele. Tyrosinase-related protein-1 (TYRP1) is the gene assigned to the B locus, and the Tyrp1 enzyme has been shown to be involved in the synthesis of the eumelanin pigment. Brown coat color phenotypes are caused by mutations in tyrosinase-related protein-1 (TYRP1) and are recognized in many mammals. This mutations can be used to identify carriers of brown phenotypes in the domestic cat. Domestic cats have a suggested allelic series, B > b > bl.