Skip to content

B-Locus (black/brown)

Original price £42.00 - Original price £42.00
Original price
£42.00 - £42.00
Current price £42.00

The B-Locus is a region of your dog's DNA which controls whether your dog has a brown coat colour. The region produces a protein which alters the colour of your dog's coat and skin. 

There are three alleles, or mutations, present in the B-locus which cause your dog's coat colour to be brown; bs, bd, and bc. If your dog has inherited any two of them with one coming from each parent then this will cause a brown coat to be expressed. The wild type black coat colour (B) is visible if no copies of bs, bd, or bc are present, or if only one copy of either bs, bd, or bc is present. If your dog only has one copy of bs, bd, or bc, then they carry brown and have the potential to produce brown puppies if mated with a brown or brown carrying dog. 

Also known as liver or chocolate, and in some breeds, such as the Dobermann and Australian Shepherd, is referred to as red. 

Your dog can only be brown if they are also E/E or E/e at the E-Locus, and KB/KB or KB/ky at the K-Locus.

The black or brown colourations are caused by mutations on the TYRP1 gene. Brown is recessive meaning two copies of b are required to alter the black colouration to brown.

Please note there are two ways of getting chocolate in French Bulldogs. This B-locus (sometimes known as testable chocolate) and the Cocoa-locus (sometimes known as untestable chocolate). We do not currently offer the Cocoa test.


Your results will be reported as one combination of the B-locus alleles with the following interpretations.

B/B - black
B/b - black carrying brown
b/b - brown


Scientific references:

Schmutz SM, Berryere TG and Goldfinch (2002). TYRP1 and MC1R genotypes and their effects on coat color in dogs. Mamm Genome 13, 380-387