Within the Cat Fanciers Association (CFA), Tonkinese, Siamese, and Burmese have
the same basic four colors although they are called by different names. Other cat
associations allow a wider variety of colors, but this article will not address
those colors.
When I began breeding Tonkinese I knew the four color names, but I became very
confused about the genetics behind them. After I read (and reread a number of times
) the Book of the Cat, it became clear. Why the confusion? Because many breeders
used inaccurate terms when discussing the inheritance of color.
The following discussion applies to Siamese and Burmese as well as Tonkinese. Only
the color names change - not the genetics.
Every cat has many thousands of genes. Except for the sex-linked genes, cats have
two copies of each gene. They inherit one copy from each parent. The basic coat
colors are created by two genes, each of which has two alleles. In this case, a
gene is a set of instructions (found at a specific location on a chromosome)
that tells the cat's body how to make the coat color. Each of the two genes
governing coat color provides instructions for a different step in the production
of color. Both steps must be done correctly for coat color to be produced in a
normal fashion. An allele is the instructions for what the gene actually says.
Thus, because the two color genes each have two alleles, there are two versions
of instructions that tell the cat's body how to make the color at one step and
two versions affecting what to do at the other step in color production. There
are: 2 genes x 2 alleles = 4 possible combinations of instructions that can be
followed. The combinations of alleles (instructions) result in different
effects on the coat colors. Gene 1 alleles result in either Black (B) or brown
(b) pigment, depending on whether B allele or b allele instructions are followed,
and Gene 2 is Dense (D) or dilute (d). In other words, Gene 1 basically effects
the hue of the pigment and Gene 2 effects the density or lightness/darkness of
the hue of Gene 1. The four combinations and their respective color names by
breed are:
| Color Names by Breed |
| Genetic name |
Tonkinese name |
Siamese name |
Burmese name |
| Black Dense |
Natural |
Seal |
Sable |
| Black dilute |
Blu |
Blu |
Blu |
| brown Dense |
Champagne |
Chocolate |
Champagne |
| brown dilute |
Platinum |
Lilac |
Platinum |
Although the Burmese call every color except Sable a dilute (as all three are
lighter than Sable), genetically a Champagne does not have the dilute gene.
Champagnes and Platinums are warmer colors than Naturals and Blues. I find it
useful to think of the colors in pairs depending on the orientation you are
thinking of.
The uppercase letter is used to denote the dominant allele and the lowercase the
recessive allele. The effect of the dominant allele will be visible in the color
of the cat's coat. The effect of the recessive allele will not be visible unless the
cat inherits two recessive alleles. This is because a dominant allele so
overshadows a recessive one that you do not see the effects of the recessive
allele. It is there but not visible. Every Tonkinese has four color genes: one
Gene 1 and one Gene 2 from each parent for a total of two Gene 1s and two Gene
2s. Neither color nor coat pattern genes are sex-linked; therefore it is
irrelevant which parent contributes the gene. Black and Dense are dominant and
brown and dilute are recessive. Again, a dominant allele will define the color
you see regardless of the second gene in the pair. For a recessive allele to
be visible, both of the pair must be the same recessive allele. Therefore,
only if both genes of a Gene 1 pair are brown will brown be the visible color.
If either gene is Black, then black will be the only color visible. The
Dense/dilute Gene 2 pair follow the same logic. Only if both genes of a
Gene 2 pair are dilute will the effect of dilute be visible.
The following table shows the different combinations that an individual cat can
have of their two genes and two alleles. Again, it does not matter which parent
contributed which gene.
| Genetic Gene Combinations by Color |
| Genetic name |
Tonkinese name |
Specific Combinations |
| Black Dense |
Natural |
BBDD, BbDD, BBDd, BbDd |
| Black dilute |
Blue |
BBdd, Bbdd |
| brown Dense |
Champagne |
bbDD, bbDd |
| brown dilute |
Platinum |
bbdd |
If a cat shows the effects of either Black or Dense or both, then the cat has
unknown, hidden or passive genes that are not visible when examining the cat. This
is because it takes only one copy of the Black or Dense allele to determine the
color. The second allele of the gene pair is the hidden or passive gene, because
it does not have any visible effect on the color. It could be the same dominant
allele or it could be the recessive allele. We say a cat carries the passive or
hidden gene. It sort of goes along for the ride but is not the driver nor even
a back seat driver. It is strictly a passenger that remains quiet (I know I'm
not a hidden gene). All four Natural's genetic combinations in the above table
would look alike, but three carry one or two hidden/passive genes.
You can sometimes use logic and knowledge of the color of the parents to determine
what hidden alleles are carried by their offspring. For example, if a Natural
Tonkinese has one parent that is a Champagne, the Natural must carry a hidden
brown (b) allele. The Champagne parent had to pass one copy of Gene 1 to each
offspring - and the Champagne could only donate one of two brown alleles. However,
knowing that one parent is a Champagne does not tell the breeder anything about
the dilute allele, because dilute can be hidden in Champagnes. A Platinum parent
is more helpful because Platinums carry no hidden genes and must always donate
one b and one d allele to each kitten.
It should now be obvious there is no Blue color gene just as there is no Champagne,
Platinum, or Natural color gene. All four colors are a combination of two genes.
I frequently hear breeders say a cat carries Blue referring to the hidden gene.
The hidden gene is not blue as blue is a combination of two colors. This is
inaccurate and confusing for others. A Tonkinese can carry both brown or dilute
not blue.
Because hidden genes affect the color of the offspring they are of great interest
to a breeder. A Natural with the BBDD combination will create 100% Naturals
regardless of to whom it is bred. Whereas Naturals with a hidden recessive allele
can create other colors. Left to nature, Naturals occur most frequently in a
Tonkinese population because they carry the dominant alleles. Platinums are
the most infrequent due to their doubly recessive gene requirement.
If you have wanted a Natural or Blue and found them in short supply, it is because
breeders have overridden nature and controlled what colors are produced by carefully
chosing the breeding pair. Why? Platinums followed by Champagnes are the most
popular with judges and many breeders want winning show cats. Of course
some breeders simply prefer those colors themselves. Some would say Platinums
are flashy. Do blondes have more fun? Blues are subtle and as discussed in the
coat pattern discussion below, they naturally have the least contrast. I find
prospective pet owners either love or dislike blues with no middle ground.
Naturals are very popular with pet owners but less so with judges.
