About the Colour
A mutation in the Brown gene (tyrosinase-related protein-1, TYRP1) results in the Chocolate coat colour.
The B allele is wild-type and produces a normal colouration, the mutant b allele produces a chocolate colouration. The mutation is recessive, hence two copies of the b allele are required for chocolate colouration.
A mutation in the Brown gene (tyrosinase-related protein-1, TYRP1) results in the Chocolate coat colour.
The B allele is wild-type and produces a normal colouration, the mutant b allele produces a chocolate colouration. The mutation is recessive, hence two copies of the b allele are required for chocolate colouration.
Interpretation of results
Test Result |
Interpretation |
Chocolate (b/b) |
Has two copies of the Chocolate allele (b/b). Cat is Chocolate. |
Carrier of Chocolate (B/b or b/b|) |
Has one copy of the Chocolate allele. Cat is Full colour (B/b) or possibly Chocolate if the cat also carries Cinnamon (b/b|). |
Does not carry Chocolate (B/B, B/b| or b|/b|) |
Has no copies of the Chocolate allele. Cat is Full colour (B/B, B/b|) or possibly Cinnamon(b|/b|). |
Lilac colouration - Ragdolls
Lilac is the result of the Dilute gene working on the Chocolate gene. The results must be Chocolate (b/b) and Dilute (d/d) for the Ragdoll to be Lilac
Lilac coluration - British Shorthair
Lilac is the result of the Dilute gene working on the Chocolate or Chocolate and Cinnamon
genes.
The results must be Chocolate (b/b) and Dilute (d/d) or Chocolate carrying Cinnamon (b/b|) and Dilute (d/d) for the British Shorthair to be Lilac.
The genetics of Chocolate, Cinnamon and Dilute colours
The Brown gene
The Brown gene has three alleles (B, b and b|), with B dominant to b, and b dominant to b|. When B is present (BB, Bb or Bb|) the coat colour is its normal, full colour. If a cat is bb or bbl the brown is lightened to chocolate. When a cat is b| b| the colour is further lightened to cinnamon.
Chocolate, Cinnamon and Dilute Colours
Chocolate/Cinnamon |
Dilute |
Coat colour |
BB or Bb or Bb| |
DD or Dd |
Black/Brown |
BB or Bb or Bb| |
dd |
Blue |
bb or bb| |
DD or Dd |
Chocolate |
bb or bb| |
dd |
Lilac |
b|b| |
DD or Dd |
Cinnamon |
b|b| |
dd |
Fawn |
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