Genetic basis of B Locus for Siberian Husky - corresponds to the TYRP1 gene, which controls the production of eumelanin pigment responsible for black or brown coloration in the coat, nose, and footpads. Siberian Huskies have multiple known variants (alleles) at the B Locus, including the recessive brown alleles: bc, bs, bd, and a breed-specific bh allele. The bh allele is unique to Siberian Huskies, in addition to the common brown alleles found in many breeds. Dogs must inherit two copies of any combination of these recessive brown alleles (e.g., bh/bh, bc/bs, bd/bh) to express the brown/liver/chocolate pigment phenotype. Dogs with only one copy of a brown allele and one copy of the dominant black allele (B) will appear black but be carriers capable of passing on brown alleles.
Inheritance Pattern - The brown color trait at the B Locus is autosomal recessive. A dog must be homozygous or compound heterozygous for recessive brown alleles to have a brown coat, nose, and footpads. Heterozygous dogs (carriers) appear black but can produce brown offspring if bred to another carrier.
Expression in Siberian Husky - The brown/aluminum brown or liver pigment is less common but recognized in Siberian Huskies. Combination of any two recessive alleles of bc, bs, bd, or bh leads to brown coloration. The presence of the bh allele is a notable Siberian Husky-specific brown variant. All brown Siberian Huskies still require proper functioning E and K loci alleles to express eumelanin in their coat.
Summary - The B Locus in Siberian Huskies involves the TYRP1 gene with four recessive brown alleles identified: bc, bs, bd, and bh (the latter specific to the breed). Expression of brown coat, nose, and paw pad pigmentation requires two recessive alleles. Genetic testing guides breeders in managing coat color inheritance to meet breed standards or personal breeding goals, balancing health and diversity.