Coat color genetics part II: B-locus (Brown and Black)

by Annika Farstad
© 2006

B-locus is a pigment locus that allows for black & brown (chocolate/liver) where the brown is a result of black (eumelanin) pigment modification.

This is a very simple gene with just two alleles and dictates the colour of all dark pigmented areas: Nose, eyerims, skin, coat. All researchers agree that the B-b series is very clearcut. Black is dominant to brown.

(B) black: In black (B) dogs the dark pigment will be black. However, this does not mean that the dog's coat will be black. Dark pigment can be restricted by genes in other series. If the dog has a black nose, it is B.

(b) liver: Black pigment is lightened to liver. Anything that would normally be black will be turned brown! So noses and pigment of liver dogs are brown, and if the dog's coat is "genetically black" (see K locus) that will also appear as brown. Like black, the coat of the dog will not necessarily be brown though, the colour may be influenced by other series. Liver (b) being recessive to black (B), two liver dogs cannot produce puppies with black pigmentation. The eye colour of a liver tends to be lighter.

A black (BB or Bb) powderpuff and hairless

Two sable (A^y) and two Cream (ee) powderpuffs. One has black pigment (B-), the other brown pigment (bb)