B-Locus bs, bd, bc (Black, Brown)

TYRP1, or tyrosinase-related protein 1, is a protein that plays a role in the synthesis of the pigment eumelanin. In the dominant form of this gene, or the "B" allele, normal eumelanin is produced in the coat, and the dog's coat appears black in color. A mutation in the TYRP1 gene can occur causing a change in function which dilutes the black color pigment to a brown color. This mutated gene is known as the "b" allele. When a dog is homozygous for the mutation, meaning he has 2 copies of the recessive allele, the dog's coat color will be brown in color. This color can also be referred to as liver, chocolate, or in some breeds, red.

B - controls the black coat color
bs, bd, bc - controls the brown coat color

The black (B) allele is dominant to the brown alleles (bs, bd, bc). In this gene (bs, bd, bc) are 3 common mutations which result in brown instead of black eumelanin production. In some breeds additional mutation not identified may affect eumelanin production.

Because TYRP1 is only associated with eumelanin, this mutation only has an effect on coat color of dogs that are "EE" or "Ee" at the E-locus. Dogs that are "ee" only produce phaeomelanin in their coats, so a mutation at the B-locus will not have an effect on their coat color. However, eumelanin is still produced in the foot pads and noses of dogs which are yellow to red (e/e at MC1r), so the B-locus still has an effect on these areas. Dogs that are "eebb" will have a brown nose and foot pads, rather than black. TYRP1 mutations affect the nose and pad coloration, changing it from black to brown. Yellow lab puppies can have black or brown noses, but Vizslas always have brown or flesh colored noses.

Example: Australian Shepherds with brown nose (caused by bb genotype)
Genotype Coat color Nose Color Transmission of Coat Color
EEbb brown (red)
brown-and-white (bicolor)
brown tricolor
Eebb brown (red)
brown-and-white (bicolor)
brown tricolor
brown red
eebb pure red
red-and-white (bicolor)
red tricolor

Genotype Coat color Nose Color Transmission of Coat Color
eeBB red
eeBb red
Black brown
eebb red

B Locus Testing:
Animal Genetics currently offers a test for the B-Locus to determine how many copies of the recessive (bS, bd, bc) allele a dog carries.

Dogs can be DNA tested at ANY age

Breed Breed Color Two Copies of Allele
Australian Shepherd red bs, bd
Border Colllie Brown bs, bd, bc
Chesapeake Bay Retriever Brown, Sedge, Deadgrass bs, bc
Chinese Shar-Pei Chocolate, Lilac bs, bc
Cocker Spaniel Brown, Liver bs, bd, bc
Dachshund Chocolate bs, bd
Dalmatian Liver bs, bd, bc
Doberman Pinscher Red bd
English Setter Liver Belton bs
English Springer Spaniel Liver bs, bd
English Pointer Liver bs, bd
Field Spaniel Liver bs, bd, bc
Flatcoated Retriever Liver bs, bd
French Brittany Spaniel Liver bs, bd
German Shorthaired Pointer Liver bs, bd, bc
German Longhaired Pointer Liver bs, bd, bc
German Wirehaired Pointer Liver bs, bd, bc
Italian Greyhound Isabella, Chocolate bc
Labrador Retriever Chocolate bs, bd, bc
Large Munsterlander Brown bs, bd, bc
Newfoundland Brown bs, bd, bc
Poodle Brown, Cafe-au-lait bs, bd, bc
Portuguese Water Dog Brown bs, bd
Pudelpointer Liver bs, bd, bc
Small Munsterlander Brown bs, bc
Weimaraner Mouse-gray bs, bd, bc

Sample Type:
Animal Genetics accepts Buccal Swab, Blood, and Dewclaw samples for testing. Sample collection kits are available and can be ordered at Test Now.

Testing is Relevant For The Following Breeds:
All Breeds.

Animal Genetics offers DNA testing for dominant B allele. The genetic test verifies the presence of the mutation and presents results as one of the following:

B/b-Allele Results:
B/B Black The dog carries two copies of the dominant B allele. The dog will have a black-based coat, and will always pass on the "B" allele to any potential offspring. All offspring will also be black-based dogs
B/bs, bd, bc Black Both the dominant and recessive copies of the B allele are present. The dog will have black-based coat, but carries the allele responsible for the brown phenotype. The dog can pass on either allele to potential offspring.
bs, bd, bc/
bs, bd, bc
Brown Two copies of the recessive allele are present. The dog has a brown-based coat, as well as a brown nose and foot pads, and will always pass on the recessive allele to all potential offspring.

To Submit a Sample For Testing:
Please download a submission form, or order canine sample collection kits at Test Now.

Mail samples to:
Animal Genetics UK,
PO BOX 107, Truro,
Cornwall, England.
TR1 2YR.

Animal Genetics UK
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