The Siamese and Burmese coat patterns are controlled by the gene TYR (tyrosinase) which produces an enzyme that is required for melanin production. The Burmese pattern is a result from reduced pigment production changing black pigment to sepia and orange to yellow. The Burmese points are darker than the body and the eyes are yellow-gray or yellow-green. The Siamese pattern shows reduced pigment production to the points and the eyes are blue. This gene is also known as Color gene or C-locus. The Coat Colour Siamese (K758) and Coat Colour Burmese (K759) combined reveal the genetic status of the C-locus. The C-locus has three variants (alleles). The C allele is dominant over the alleles cb and cs; allele cb is semi-dominant over allele cs. The dominant allele C does not have an effect on the coat colour. Two copies of the cb allele (homozygous cb/cb) results in a Burmese coat pattern. One copy of the allele cb and one copy of the allele cs (cb/cs) result in the intermediate mink colour. Two copies of the cs allele (cs/cs) results in a Siamese coat pattern.
The Coat Colour Siamese and Coat Colour Burmese tests (together C-locus) enclose the following results:
Siamese | Burmese | C-locus | Coat Colour |
---|---|---|---|
N/N | N/N | C/C | Full colour |
N/N | N/cb | C/cb | Full colour |
N/N | cb/cb | cb/cb | Burmese / Sepia |
N/cs | N/N | C/cs | Full colour |
N/cs | N/cb | cb/cs | Tonkinese / Mink |
cs/cs | N/N | cs/cs | Siamese / Pointed |
In the following scheme the results of the C-locus are shown in combination with the possible results for the B-locus and D-locus:
C-Locus | B-locus | D-locus | Coat Colour |
---|---|---|---|
C/C | B/B, B/b or B/b’ | D/D or D/d | Black |
C/C | B/B, B/b or B/b’ | d/d | Blue |
C/C | b/b or b/b’ | D/D or D/d | Brown, chocolate |
C/C | b/b or b/b’ | d/d | Lilac |
C/C | b’/b’ | D/D or D/d | Cinnamon, Red |
C/C | b’/b’ | d/d | Fawn |
C/cb | B/B, B/b or B/b’ | D/D or D/d | Black |
C/cb | B/B, B/b or B/b’ | d/d | Blue |
C/cb | b/b or b/b’ | D/D or D/d | Brown, chocolate |
C/cb | b/b or b/b’ | d/d | Lilac |
C/cb | b’/b’ | D/D or D/d | Cinnamon, Red |
C/cb | b’/b’ | d/d | Fawn |
C/cs | B/B, B/b or B/b’ | D/D or D/d | Black |
C/cs | B/B, B/b or B/b’ | d/d | Blue |
C/cs | b/b or b/b’ | D/D or D/d | Brown, chocolate |
C/cs | b/b or b/b’ | d/d | Lilac |
C/cs | b’/b’ | D/D or D/d | Cinnamon, Red |
C/cs | b’/b’ | d/d | Fawn |
cb/cb | B/B, B/b or B/b’ | D/D or D/d | Sable, Seal Sepia |
cb/cb | B/B, B/b or B/b’ | d/d | Blue Sepia |
cb/cb | b/b or b/b’ | D/D or D/d | Chocolate Sepia, Champagne |
cb/cb | b/b or b/b’ | d/d | Lilac Sepia, Platinum |
cb/cb | b’/b’ | D/D or D/d | Cinnamon Sepia |
cb/cb | b’/b’ | d/d | Fawn Sepia |
cb/cs | B/B, B/b or B/b’ | D/D or D/d | Seal Mink, Natural Mink |
cb/cs | B/B, B/b or B/b’ | d/d | Blue Mink |
cb/cs | b/b or b/b’ | D/D or D/d | Chocolate Mink, Champagne Mink |
cb/cs | b/b or b/b’ | d/d | Lilac Mink, Platinum Mink |
cb/cs | b’/b’ | D/D or D/d | Cinnamon Mink, Honey Mink |
cb/cs | b’/b’ | d/d | Fawn Mink |
cs/cs | B/B, B/b or B/b’ | D/D or D/d | Seal Point |
cs/cs | B/B, B/b or B/b’ | d/d | Blue Point |
cs/cs | b/b or b/b’ | D/D or D/d | Chocolate Point |
cs/cs | b/b or b/b’ | d/d | Lilac Point, Platinum Point |
cs/cs | b’/b’ | D/D or D/d | Cinnamon Point |
cs/cs | b’/b’ | d/d | Fawn Point |