here are many factors that affect coat colour and pattern in domestic cats and a bewildering array of colours and pattern combinations now exist across the range of various pedigreed breeds. There is also huge variation in hair 'type' ie; long hair, short-hair, hairless, rex (curly) etc.

The intention of this page is to provide some genetic background of this fascinating breed, the Tonkinese, and to share some facts about the genetics of Coat Colour inheritance in domestic cats as a whole - This is not a complete analysis of coat colour genetics (see Links page) but is primarily focused on the genetics that underpin theTonkinese breed. 

I try not to blind with science, all too often I'm met with a blank stare from other breeders when the subject of genetics arises, yet with a little effort it is easy to understand the genetics that underpin the breed and the resulting patterns of inheritance.......

..... so let's start with the basics;

The expression of Coat Colour in all cats is mainly determined by two key factors;
These two factors are;

1) The base colour of the coat (of which there are only 4 basic colours) All other 'self' colours are modifications of these. These colours are referred to as having ‘Dense’ colour expression.     
1 - Black     
2 - Brown     
- Cinnamon     
4 - Red

The 4 basic colours may be modified by a diluting gene to create 4 new colours; These are referred to as ‘Dilute’ colours.
1 - Black = Blue     
2 - Brown = Lilac
3 - Cinnamon = Fawn
4 - Red = Cream

The 4 diluted colours may be further altered by a gene to create 4 additional variations of colour. These are known as 'Dilute-modifier' colours.      

1 - Blue = Blue-based Caramel    
2 - Lilac = Lilac-based Caramel
3 - Fawn = Fawn-based Caramel    
4 - Cream = Apricot

2) The Pattern or distribution of that colour 'Patterns' come in many varieties and are controlled by a great diversity of genes and we might also refer to these as 'markings'     
elf/Solid (one evenly toned colour)     
Ticked, etc.

These Patterns may then be modified further by additional genes that alter the expression of the base pattern, such as;

White-spotting gene -
often combined with other patterns to create bi-colour cats. The white spotting gene is present in all cats that have patches of white, whether it be the classic black and white moggie or the highly bred ragdoll, the same gene masks the pigment of cat with areas of pure white that show no pigmentation.

Himalayan (colourpoint) - although most commonly associated with the modification of 'self or solid' colours the Himalayan gene may be combined with any of the above patterns, therefore 'overlaying' the base pattern; ie; 'tabby-point', Tortie point etc, to result in a pointed cat with additional markings.



 Naming System for Feline Coat Colour & Pattern

In terms of an identification system for colour and markings, most cats are described in terms of the colour name first and then pattern name second - ie; blue-tabby, lilac-point etc.

Adding to the potential confusion with identifying colours, different breeds utilise different naming systems for the same colours, ie; black may be called 'ebony' in some breeds and is expressed as Seal in Tonkinese. Brown may be called 'chocolate' and thus it can be very confusing to determine which of the 4 basic colours a cat possesses, but regardless of the colour name, all cat coat colours fall under one of the 4 basic colours that may have been altered further by with modifications genes, and all have a pattern (even if the pattern is 'plain' ie 'self/solid-colours')

Looking at the Siamese/ Oriental breeds - the following examples show the colour name and their genetic influences that create radically different results in the appearance of the cat.

Black Oriental
Genetic Colour Profile
Colour = Black
Pattern = Self

Chocolate Oriental
Genetic Colour Profile
Colour = Black
+ mutation for brown
Pattern = Self

Seal-Point Siamese
enetic Colour Profile
Colour = Black
Pattern = Self
+ Himalayan pattern

Chocolate Point Siamese
Genetic Colour Profile
Colour = Black
+ mutation for brown
Pattern = Tabby pattern
+ Himalayan pattern

It is therefore possible for a cat to have multiple genes for colour & pattern interacting with one another.

Many breeds allow for multiple pattern genes in their standard.

Lilac-Lynx Bi-Colour Ragdoll
This cat displays 3 genes for mutation of colour, and 3 additional genes that contribute to the 'pattern'.

Genetic Colour Profile
Colour = Black
+ mutation = brown
+ dilution = lilac

Pattern = Tabby pattern
+ Himalayan pattern
+ White-spotting

This Ragdoll displays multiple genes for colour & pattern.

Thus a Tonkinese is identified also by the same two factors;

COAT COLOUR - Will be one of 4 main colours
or their dilute versions.

Blue (diluted Black)
Chocolate (Brown)
Lilac (diluted Brown)
Fawn (diluted Cinnamon)
Red or
Cream (diluted Red)


PATTERN = Self + Himalayan / Colourpoint (variations between contrast of points and body colour) ie;

Solid (low contrast) 
Mink (medium contrast) or
Point (high contrast)

A Tonkinese is thus identified by both colour and pattern, the pattern being of the Himalayan series but defined as which of the 3 versions of the Himalayan gene that is being expressed.

Thus a Seal-coloured Tonkinese can be either a Seal-Solid, a Seal-Mink or a Seal-Point





The main colours bred in Australia

In Australia the main four colours Seal, Chocolate, Blue & Lilac have been bred since the breed was first developed. At Anniesong we have now introduced another 2 colours with the addition of Cinnamon & Fawn to the Australian repertoir of colours available in the Tonkinese. 

Until recent times the pattern associated with the breed in Australia has been almost exclusively been the 'self' pattern that has been modified by the Himalayan gene. And although the 'self' pattern combined with the Himalayan gene is most prevalent and popular, there are other lesser known patterns that also are permitted  within different breed registries.

The colour 'Seal' & it's dilute 'Blue'

Seal is the original colour that defined the Siamese, Burmese & Tonkinese breeds.

Although appearing as a very dark brown on all three breeds, genetically Seal is Black that has been modified by the Himalayan Gene, whereby the shape of the melanin has been altered and this has the effect of black appearing as a weaker expression that results in the rich dark tone we know as Seal.

Blue, as the dilute of Seal was the first colour to appear in Siamese and Burmese lines after the breeds were established with Seal being the defining colour of both breeds. It is possible this derived originally from the Korat, also a native breed of Thailand where the expression of black has been modified to appear as blue.

The Colour Blue displays the least contrast, and its' not unusual for a Blue-Mink to appear as having no points, but as a more even shade of blue/grey from point-body tone.


Tonkinese Colour name = Seal

Genetic Colour Profile
Colour = Black
Pattern = Self
+ Himalayan pattern


Tonkinese Colour name = Blue

Genetic Colour Profile
Colour = Black
+ Dilution = Blue
Pattern = Self
+ Himalayan pattern


The colour 'Chocolate' & it's dilute 'Lilac'

Chocolate is derived from a mutation of the Black gene, and first appeared in the gene pool of the Siamese. Originally thought to have come from the Siamese breed and developed as a Self-colour (oriental) to become a stand-alone breed that was called the 'Havana cat'. Chocolate is now an accepted colour in many breeds.

Where there is no Himalayan gene in place and therefore no points, the colour chocolate appears as a bright and rich dark brown, but expresses in a more muted tone on Siamese, Burmese & Tonkinese, this is due to the slight 'weakening' of colour that happens when the Himalayan gene is active.

With the Himalayan gene in place, Chocolate expresses with greater contrast between body colour and that of the points, the Chocolate-Solid is therefore the least 'solid' and points are still quite apparent.

Lilac as the dilute of Chocolate is also very contrasty and a Lilac-Solid will also still have evidence of pointing.


Tonkinese Colour name = Chocolate

Genetic Colour Profile
Colour = Black
+ mutation for brown
Pattern = Self
+ Himalayan pattern


Tonkinese Colour name = Lilac

Genetic Colour Profile
Colour = Black 
+ mutation for brown
+ dilution = Lilac

Pattern = Self
+ Himalayan pattern


The  NEW colour 'CINNAMON' & it's dilute 'FAWN'

Cinnamon & Fawn are relatively new colours and now appear in Siamese, Burmese & Tonkinese breed standards. Cinnamon derives from a further mutation of the Chocolate gene.

Cinnamon appears as a warm and light brown, and is a colour that is slow to develop, so takes a long time before full expression of the colour is seen.

First accepted as part of the Siamese breed standard, in the breeds of Burmese and Tonkinese there has been a rocky road to their acceptance here in Australia. They are accepted in the New Zealand, USA, some of Europe but not the UK.

Fawn is a very delicate colour, and is warmer and lighter in tone than Lilac.
And like it's Cinnamon counterpart, the colour Fawn is very slow to develop and is often challenging to distinguish from Lilac unless seen together.



Tonkinese Colour name = Cinnamon

Genetic Colour Profile
Colour = Black
+ mutation for Cinnamon
Pattern = Self
+ Himalayan pattern


Tonkinese Colour name = Fawn

Genetic Colour Profile
Colour = Black
+ mutation for Cinnamon
+ dilution = Lilac

Pattern = Self
+ Himalayan pattern


So what is the HIMALAYAN GENE ?

Also referred to as the ‘Colourpoint gene’, the Himalayan gene was originally a mutation of the ‘self’ or ‘solid’ patterns, and results in the colour of the cat to only be expressed fully on the extremities, fading to a lighter tone on the rest of the body. The effect is referred to as 'Colour-Restriction'

and what is meant by COLOUR RESTRICTION ?

The patterns that define Burmese, Siamese & Tonkinese are referred to as; ‘colour restriction patterns’ and all are controlled and determined by the ‘Himalayan gene’

Colour restriction – or the limiting of colour expression to the extremities of the cat’s body is caused by the Himalayan gene. Genetically, all self-coloured Tonkinese regardless of colour and pattern, are actually black cats. However the Himalayan gene inhibits the full expression of the pigment on most of the cat's body. The effect of the gene is that most of the colour is 'bleached' or 'faded' and the deteremining factor is body temperature (see below)

and its not just cats .....

The Himalayan gene generally occurs most usually within domestic rodent species, and is most commonly seen in rabbits, guinea pigs and mice.

It is thought to have derived its name from the fact that the first of their kind was seen in domestic rabbit breeds from the Himalayan region.

Domestic Rabbit - sourced image 

Believed to be the first domestic animal to display the Himalayan pattern.

Domestic Guinea Pig - sourced image 

The Guinea Pig (or Cavy) originates from South America and is also a domestic rodent that comprises the Himalayan gene.

Domestic Mouse - sourced image

 Some interesting facts about how the Himalayan gene works in Cats
  • The Himalayan generally occurs most usually within domestic rodent species, and is most commonly seen in rabbits, guinea pigs and mice.
  • The melanin in their hair and skin is temperature sensitive, controlling the points on the cat's body.
  • In addition to limiting where the colour will be expressed, the Himalayan gene tends to "bleach out" the colour to varying degrees, depending on the form of colour restriction; ie; Pointed/Mink/Solid.
  • The gene also has a weakening effect on colour. The colours seen on the points of Himalayan breeds are less vibrant than their counterparts when the Himalayan gene is not present. ie; seal (very dark brown ) is actually the gene for black and appears as jet black if not combined with the Himalayan gene.
  • The longest-established and best known of these is the Siamese breed, which was used to incorporate the Himalayan gene into other breeds that now express this pattern.
  • It may seem odd to think of Tonkinese as solid colour cats, but genetically they are; they have just had a "special effect" overlaid on them.

The 3 variations of Himalayan Gene

Tonkinese, Burmese & Siamese breeds all express variations of  the ‘Himalayan Gene’ series.

The 3 variations on the Himalayan gene are intrinsically linked and create the 3 patterns known in Tonkinese as; Solid, Mink & Point.

  • In a Tonkinese the 'Solid' pattern is identical to the pattern for Burmese from which it derives its pattern. This pattern expresses the least contrast between the point and body colour.
  • The 'Point' pattern is thus the pattern of the Siamese, and has the most contrast between point and body colour.
  • The 'Mink' pattern the result of a mating of a solid to a Point, and was the defining pattern of the Tonkinese originally, before the breed standard allowed for both points and solids to be accepted.


Of the 3 breeds that each display the Himalayan gene, the Tonkinese is the only breed that allows for all 3 versions creating 3 distinctive patterns.

In essence the colour/pattern shared between the two breeds differ only in degrees of contrast, with Solid-pattern showing the least contrast (darkest body), Point-pattern showing the most contrast (lightest body), and the Mink-pattern having a contrast range / body-tone between the other two.

This is due to neither the gene for Siamese Pattern or the Burmese Pattern being ‘dominant’ - instead they are described as co-dominant. This genetically ‘unusual’ mode of inheritance is referred to as ’Incomplete Dominance'. Where unlike genes for many colour / pattern traits there is not the dominant and recessive gene relationship.



So what is 'Co-Dominance' as a genetic mode of inheritance?

Co-dominance (also called partial dominance) occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. Co-dominance occurs when the contributions of both alleles are visible in the phenotype.

So how does Co-Dominance affect coat colour and pattern in the Tonkinese?

The two alleles that determine coat pattern in the Tonkinese breed are cs (the allele for the Siamese coat pattern) and cb (the allele for the Burmese coat pattern).

Both alleles are from the albino series, and cause unstable pigment colouration, due to temperature sensitivity of the melanin. This results in greater colouration on the cooler parts of the body, or the points (the extremities).

The torso has a lighter colouration because body temperature is higher there. The amount of contrast between the extremities and the torso varies from a very strong contrast in the Siamese coat pattern cscs to a very weak contrast in the Burmese coat pattern cbcb.

When we have a Tonkinese with both cs and a cb (genes come in pairs - one from each parent), we get a third variation which we call a mink cscb. Because neither is dominant over other, they are co-dominant. We achieve a coat pattern part way between the other two in terms of contrast.

A Tonkinese created from a Siamese and a Burmese mating, (or from a Solid x Point Tonkinese mating for that matter) will have a different genetic code for colour than it's parents, due to the co-dominance of the alleles for coat patterns.

Siamese (high contrast) = cs
(low contrast) = cb
(mid contrast) = cscb
(high contrast) = cscs
Tonkinese-Solid (low contrast) = cbcb

As all genes are coded in pairs, each parent contributes one gene for any particular trait to its offspring, meaning that all progeny from this mating will inherit one gene for Siamese Colour-restriction, and one for Burmese Colour-restriction, resulting in a Mink-patterned kittens only.



When two mink-patterned cats are mated together, there are 3 potential combinations possible, and while there is no guarantee that all three patterns will appear in one litter, the probability is for twice the number of Mink-patterns than that of Solid and Point patterns - so why is that?

When it comes to the inheritance of coat colour each Mink-patterned parent contributes one gene each, and as they both comprise genes for both Point and Solid patterns, the 3 patterns become possible in their progeny as the pairs of genes in each case recombine.

Statistically 50% of the time the offspring inherit a combination, one gene for Point (cs) and one for Solid (cb), resulting in a Mink (cscb) kittens.

25% of the offspring will inherit two copies of the gene for Point (cs) resulting in a Point-patterned kitten (cscs)

Consequently 25% of the offspring will inherit two copies of the gene for Solid (cs) resulting in a Solid-patterned kitten (cscs)


When a Mink-patterned cat is mated with a Point-patterned cat, the probability is for equal numbers of both the Mink and Point patterned kittens.

The probability is due to neither pattern being dominant over the other and the possibility of 50/50 balance between numbers of each pattern - this again is not guarantee, just an indication of likelihood.

A litter of 6 kittens from such a mating could thus still produce all one pattern, but we know that this mating can never produce a Solid-patterned kitten.


When a Mink-patterned cat is mated with a Solid-patterned cat, the probability is for equal numbers of both the Mink and Solid-patterned kittens.

The probability is due to neither pattern being dominant over the other and the possibility of 50/50 balance between numbers of each pattern -

And while the balance between the two patterns is variable, we can deduce that this mating can never produce a Point-patterned kitten.



So how rare is Co-Dominance as a genetic mode of hereditary ?

The usual mode of inheritance where one gene will dominate and therefore 'hide' the effect of the recessive gene, is common to how many traits are inherited. But Co-Dominance and the resulting expression of colour does occur in other domestic animals, albeit rarely. As seen below in the Palomino horse, a colour that is due to a co-dominant mode of inheritance.

'Co-Dominance' - is a genetically unusual mode of inheritance and is seen in the other domestic animals as it applies to some colour genes. The general effect will be a blending of effect between the two parental colours.

The 'Cremelo' gene combined with the gene for chestnut and creates an intermediate form ie; Palomino.

Chestnut Horse

The Chestnut coloured horse displays no 'dilution gene' and therefore it's colour is unaffected by this potential influence.

Two Chestnut horses bred together
will only produce Chestnuts and can never produce a Palomino or a Cremelo.

Palomino Horse

The Palomino is the result of having 1 gene for colour from each parent, thus having one gene for cremello and 1 gene for chestnut, results in a 'blend' of the two colours being expressed.

The of probability ratio when breeding two Palomino horses together is 1/4 Chestnut, 1/2 Palomino & 1/4 Cremello

Cremelo Horse

The Cremelo carries 2 copies of a gene that lightens the base colour, and when combined with other colours produces an intermediate blend of the parental colours results.

Two Cremelos bred together will only result in Cremelo offspring


How can the six Tonkinese colours that are so different in appearance all be versions of black?

The six colours bred at Anniesong Tonkinese are all genetically self ‘black’, yet they appear very differently due to genetic mutations that affect the melanin granules that determine coat and skin pigmentation.

An interaction of two key factors determines how the 6 colours identified as (Seal & Blue), (Chocolate & Lilac), (Cinnamon & Fawn) are expressed. 

These factors depend on mutations of the gene for black pigmentation that result in changes to;

  • the Shape of the melanin granules that occupy the hair shaft and skin. (determining the Base Colour / Seal, Chocolate or Cinnamon)
  • the Distribution of the melanin granules that occupy the hair shaft and skin.  (determining if colour is of dense or dilute-pigmentation)

Magnified, the melanin granules are uniform in their ‘colour’ in both the dense-pigment cats and dilute-pigment cats - Yet visibly the two factors result in drastic variations in the expression of colour.

How the colour appears is therefore dependent on the combination of the shape & distribution of the melanin granules. The melanin granules vary in how eliptical they are in shape.

The more eliptical the shape of the granules - the greater degree of lightness & warmth expressed in the tone - ie cinnamon is much warmer colour than Seal - this is due to more light passing through the gaps between the melanin granules.

In the dilute colours the more significant spaces between the clumps of melanin created further lightening and cooling effect on each of the colours.

As a result, Seal, Chocolate & Cinnamon are therefore referred to as expressing dense pigmentation, (even distribution of melanin granules)

Blue, Lilac & Fawn are referred to as expressing dilute pigmentation (clumped distribution of melanin granules), allowing more light to pass through the gaps and having a cooling (or greying) effect on how the colour appears.


So how are GENETIC CODES determined

In the field of Genetics, codes have been determined to describe the genes for both colour and pattern. We describe this as the 'Genotype.'

In each case these 'codes' are most usually determined by a series of 2 letters, due to the fact that genes for any one trait are transmitted in pairs, frequently where one of the genes dominates and 'hides' the other. Thus in each case the Dominant gene is described using a capital letter.

The gene for Seal (Black) = B
The gene for Chocolate (Brown) = b

therefore Seal is dominant over Chocolate, which is thus recessive to Seal

Thus a Seal-coloured Tonkinese that is Homozygous for Seal, ie; both genes are for the colour Seal is coded; BB
Seal-coloured Tonkinese that is Heterozygous', ie; carrying Chocolate is coded; Bb
A Chocolate-coloured cat that is homozygous; for Chocolate is coded; bb

In the diagram below we have visualised the genotypes, and the legend shows which 'carried' or hidden genes are presen t... the genotype 'code' is below the colour name in each colour panel.


The Colour Genotype is an independent factor to the 3 patterns expressed in the coat of the Tonkinese.

Therefore regardless of the pattern that is expressed on the coat, the genotype for colour will be the same.

Thus a Seal-Mink carrying the gene for Chocolate and Dilute will have the same genetic code for colour as the Seal-Point and the Seal-Solid, and therefore will all be BbDd.

However the code for the colour/pattern combination will differ as follows;

Seal-Mink = BbDd / cscb
Seal-Solid = BbDd / cbcb
Seal-Point = BbDd / cscs

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