B locus — black series
Controls: Whether the black pigment shows as black, chocolate or cinnamon.
The B locus sets the 'black series' of eumelanin. The dominant B gives black; the recessive b gives chocolate; the most recessive bl gives cinnamon. Dilution (the D locus) then softens each of these.
Alleles
BBlackDominantbChocolateRecessiveblCinnamonRecessiveBreeding examples
Black carrying chocolate (B/b) × Black carrying chocolate (B/b)
← ≈ 3 in 4 black, 1 in 4 chocolate.
Chocolate (b/b) × Chocolate (b/b)
← All kittens chocolate — a recessive bred to itself is fixed.
Black (B/B) × Chocolate (b/b)
← All kittens black, and every one carries chocolate.
Colours it produces
Frequently asked questions
Can a black cat carry chocolate?+
Yes — black is dominant, so a black cat can hide a recessive chocolate or cinnamon allele and pass it to kittens.
What is the difference between chocolate and cinnamon?+
Both are recessive to black. Chocolate (b) is a rich warm brown; cinnamon (bl) is a lighter reddish-brown and the most recessive of the three, so it is the rarest.
Why is a chocolate kitten rare?+
Because b is recessive, a chocolate kitten needs the chocolate allele from BOTH parents. Two black cats can only produce it if both secretly carry it.
Related genes
See these colours on real cats.
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