Brown (B Locus)

General Information: The B Locus, associated with the TYRP1 gene, is responsible for determining brown coat color in dogs. This genetic locus influences the production of eumelanin, the pigment responsible for black and brown coloration in the coat, skin, and eyes. Dogs with two copies of the recessive allele at the B Locus will produce brown pigment instead of black, leading to coat colors that range from light brown to dark chocolate. This trait can also affect the color of the dog’s nose, paw pads, and eye rims, resulting in a brown appearance rather than the typical black. Variations at the B Locus are common in breeds such as Labrador Retrievers, Doberman Pinschers, and Poodles. Understanding the genetic basis of coat color can help breeders predict the appearance of future litters and select for specific traits that meet breed standards or personal preferences.

Gene / Testing Information: Genetic testing for the TYRP1 gene is crucial for identifying the B Locus status in dogs, which determines if they will produce black or brown pigment. The B Locus functions in a recessive manner, meaning a dog must inherit two copies of the brown allele, one from each parent, to exhibit the brown coat color. Dogs that carry only one copy of the brown allele and one copy of the black allele will typically have black pigmentation but can pass the brown allele to their offspring. When two carriers of the brown allele are bred, each puppy has a 25% chance of being homozygous for the brown allele and displaying a brown coat, a 50% chance of being a carrier, and a 25% chance of being homozygous for the black allele. Accurate genetic testing is essential for breeders who want to predict and select for specific coat colors, ensuring they meet breed standards and avoid unexpected color outcomes in their breeding programs.