Description: The allele B (wild type) is responsible for the production of black eumelanin and is inherited predominantly against the recessive brown allele.
There are 4 different alleles at locus B: the normal allele B (dominant) and three recessive alleles bc, bs and bd. The combination of any two recessive alleles results in a chocolate-liver brown color (for example, two allele bc or one allele bc and one bs).
In the presence of two mutant alleles b, the individual produces brown eumelanin (brown, chocolate, liver, sedge, red). A study (Cargill et al., 2005) found that this locus was responsible for turning black spots in Dalmatian to brown. Any individual having at least one B allele should have a black coat color, except for those having the e / e alleles at the E locus. Individuals having two copies of any b allele will be colored brown. This locus also affects the color of the nose if one allele B is present if two alleles are present, the nose has a brown (liver) coloration.
Since the TYRP1 gene is related to eumelanin production, it affects only dogs that have the E / E or E / e genotype at the E locus. Locus B also affects the color of the nose, eyes, and paws. Dogs with the e / e genotype produce only pheomelanin, but the production of eumelanin in the nose, eyes, and paws is unaffected and is therefore completely controlled by locus B. Depending on genotypes E and B, dogs may have a yellow coat and a brown nose/eyes (e/e, b/b) or chocolate coat and brown nose/eyes (E/e or E/E and b/b).
Inheritance: autosomal recessive
Mutation: bS (Q331ter), bD (345del), bC (S41C) in TYRP1 gene
Sample: EDTA whole blood (1.0 ml) or 2 buccal brushes. For official purposes, the confirmation of the dog’s identity by Veterinarian is recommended.
The analysis is suitable for the following breeds: Australian Cattle Dog, Australian Shepherd, Bedlington Terrier, Border Collie, Brittany Spaniel, Cardigan Welsh Corgi, Chihuahua, Chinese,Shar-pei, Cocker Spaniel, Curly Coated Retriever, Dachshund, Dalmatian, Doberman Pinscher, English Cocker Spaniel, English Setter, English Springer Spaniel, Field Spaniel, Flat-Coated Retriever, Fox Terrier, German Longhaired Pointer, German Shorthaired Pointer, German Wirehaired Pointer, Labrador Retriever, Lowchen, Miniature Pinscher, Newfoundland, Pointer, Pomeranian, Poodle, Portuguese Water Dog, Pudelpointer, Scottish Terrier, Skye Terrier, Weimaraner, Wirehaired Pointing Griffon.
Notes: A new brown mutation bE c555T> G has been described and published in the Australian Shepherd breed for first time by our laboratory. Its presence has been confirmed in other breeds that have a brown color.