Burmese nature is known to be unique just like their genetic make-up.

All dominant genes have an upper case letter and all recessive genes a lower case letter. Recessive factors of inheritance can only show up in homozygous form.

A homozygous sable Burmese has following genotype:

aa cbcb BB DD ii

We would like to introduce the relevant Burmese genes as follows :

a = non agouti

A = agouti

Agouti is a pattern of pigmentation in which individual hairs have serveral bands of light and dark pigment.
In contrast hairs on non agouti cats are unbanded, producing a solid coloured coat. Non-agouti cats are homozygous for the allele aa at the agouti locus. The non-agouti gene inheritance is recessive.

cb = Burmese gene

B = gene for the colour black
The black allele B is dominant and produces a black coat. In connection with the burmese gene cb the black colour is reduced to a brown colour. Our sable burmese is genetically a black cat.

b = dark brown allele (chocolate), a mutation of the allele B, reduces black to a brown, chocolate colour.

D = dense gene - allele for non-dilution, is responsible for full pigmentation and is a dominant gene.

d = the mutation of the dense gene D is d (dilution) and modulates the intensity of the coat colour to a more pale coat. In recessive form the dense gene (dd) is known as the dilution gene as it dilutes black (sable) and chocolate to blue and lilac respectively.

i = non silver

There are four different kinds of solid colours.

Once again: the genes of a homozygous sable Burmese

aa cbcb BB DD ii

1 ) sable = a sable Burmese is genetically black: BB DD

2) blue = dilution of black is blue

3) chocolate = next to black there is brown. This is the mutated allele to black B and changes the black pigmentation into different shades of chocolate, shown by the symbol b.
Thus our chocolate cat: bb DD
That is how we get a chocolate coloured cat. Chocolate is in relation to black a recessive colour.

4) lilac = the chocolate - brown gene is diluted to bb dd
A lilac cat is homozygous for chocolate and blue. It contains the recessive allels in the genetic code.

We have four kinds of sables :

BB DD = sable ( genetically black )

BB Dd = sable, carrying blue

Bb DD = sable, carrying chocolate

Bb Dd = sable , carrying chocolate and blue

We have two kinds of blues :

BB dd = blue

Bb dd = blue , carrying chocolate

We have two kinds of chocolate :

bb DD = chocolate

bb Dd = chocolate, carrying blue

and

bb dd = lilac burmese, they do not have any dominant genes

Responsible for these colours is the gene for Orange.

An interesting characteristic of the orange gene is that it is carried on the X- chromosome, which makes it sex-linked.

The orange gene has two alleles: non - orange o and orange O.

The non - orange allel o is recessive and allows full expression of the black locus. The dominant orange allele O, however, influences expression of the black and agouti loci because it substitutes the production of phaeomelanin for eumelanin. It makes the effect of the black gene by converting a black or brown coat to orange.

In male cats this locus can produce only two phenotypes : black or orange. If a male carries the orange allele, he will be orange (red/ cream).

In females it can produce three phenotypes: black (oo), orange (OO) and tortoiseshell (Oo).

Females are XX meaning they have two X -chromosomes. If both chromosomes carry the orange allele then the coat will be orange (OO) - red/cream -. If she is heterozygous (Oo) her coat will be a patchwork of orange and black patches, called tortoiseshell.

OO DD = orange, homozygous red

Oo DD = tortoiseshell - seal-tortie and chocolate-tortie

OO dd = cream

Oo dd = tortoiseshell - blue-tortie and lilac-tortie

The gene for orange overlaps all possible colour varieties.

All these 10 colours are recognized in cat organizations worldwide.

The Burmese come without any barring and in warm colours which are generated through selective breeding.

Nowadays Burmese appear without barring and come in warm colours due to selective breeding
The warm colours are caused by the rufousing gene.
Rufousing (lat. rufus = redish brown, engl. rufous = fox red)
This term explains the wide range of yellow pigments and is as well responsible for the darker appearance of colours. The rufousing gene is representative for the contrary of the wild type (agouti). This range is indeed wide and is inherited polygenetically. The more rufousing there is in a breed the warmer are the colours.

There are efforts (as in other breeds too) to introduce the silver and agouti gene into the Burmese breed. New colours such as silver, ticked, smoke as well as caramel, apricot, fawn and cinnamon were established.
These animals appear very attractive to the eye of the beholder. Nevertheless the introduction of the silver gene creates conflicts that should not be underestimated. A show silver cat represents that kind of breeding where polygenes (rufous) will be deliberately deleted. Silver cats ought to be without any yellow pigmentation which means a colder basic colour in order to present the silver. When the rufousing genes are deleted all the Burmese colours appear cold.
That is why the silver gene is not desirable in many breeds, especially not in the Burmese breed.

Many years of breeding experience show that the silver gene minimises respectively deletes all rufousing genes.