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Tonkinese Coat-Patterns
an explanation of the
three Tonkinese coat-patterns
© Linda Vousden
The Tonkinese coat-pattern is probably the most discussed, and written about, aspect of the breed
because the genetic behaviour of the Tonkinese coat-pattern is unique among cat breeds.
Why is it unique? Because there isn't actually a gene that produces the subtle Tonkinese coat-pattern. It is caused by a quirk of nature, and can only be seen if the cat inherits a combination of two different genes from its parents - the gene that produces the pointed coat-pattern in the Siamese plus the gene that produces the self-coloured coat-pattern in the Burmese. You can read more about the genetics of the Tonkinese coat-pattern in the book Tonkinese Cats.
Normally, one variation of a gene is dominant to another (for example in the gene for hair length, short-hair is dominant to long-hair); but the Tonkinese mink coat-pattern comes about because the gene inherited from the Burmese parent (Cb) is co-dominant with the gene inherited from the Siamese parent (Cs) - ie one will never dominate the other. So they combine as CbCs to produce both of their individual effects. This means that we get an apparently self-coloured coat combined with darker points
self (CbCb) x pointed (CsCs)
inherited Cb + inherited Cs = CbCs (Tonkinese)
The next step is even more interesting. When you mate Tonkinese, with the Tonkinese coat-pattern (CbCs), together each parent is carrying both the s'solid' (Cb) and the pointed (Cs) variations of the coat pattern gene - as the kitten will inherit only one variation from each parent there are three possible coat-pattern combinations in the kittens :-
Tonkinese (CbCs) x Tonkinese (CbCs)
Cb - inherited from parent 1 Cb - inherited from parent 1 Cs - inherited from parent 1
Cb - inherited from parent 2 Cs - inherited from parent 2 Cs - inherited from parent 2
CbCb = Tonkinese CbCs = Tonkinese CsCs = Tonkinese
with the self coat-pattern with the Tonkinese coat-pattern with the pointed coat-pattern
and yellow/green eye colour and aqua eye-colour and clear blue eye-colour
Four irrational misconceptions that we still hear -
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We still read that when Tonkinese are mated together they produce Tonkinese, Burmese and Siamese - this is wrong! Tonkinese mated together can only produce Tonkinese.
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Some use the expressions Burmese-variants or Siamese-variants - this is wrong! The coat-patterns are 'solid' and pointed Tonkinese.
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Some people continue to say that the Tonkinese do not breed 'true' - this is wrong! It has come about because these people cannot (or will not) understand the meaning of the word unique - they try to fix the Tonkinese into the breeding patterns of other breeds, and so demonstrate their limited understanding of feline genetics. There is much more to a cat than just its coat-pattern. The Tonkinese breeds as consistently for type (head and body conformation), eye-colour, coat-type and character as any other breed & more so than some - it also breeds consistently for the three coat-patterns.
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The Tonkinese are just a hybrid of Burmese and Siamese. If the accepted use of the word hybrid, in the Cat Fancy, is a cross of two cat breeds then the Tonkinese are hybrids, but no more so than the - Angora, Asian, Bengal, Balinese, Bombay, Burmilla, Colour-Point BSH, Exotic, Javanese, LaPerm, Norwegian Forest, Occicat, Oriental SH, Ragdoll, Seychelloise, Snowshoe, Somali, Tibetane, Tiffanie and so on ..... ..... and the cats breeds that are not derived from a cross of two pedigree breeds were derived, at some point, from unknown non-pedigree crosses!