Again this distinctive colouring is due to a mutation of the basic black colour. The Siamese colouring is in fact just a couple of steps removed from albino pigmentation, which would result in a white animal with pink eyes (very rarely seen in cats). The Siamese colouring is also unusual in that it is temperature sensitive, meaning that in a cooler environment the cat will appear darker - this is of course why the "points" (legs, face, ears, tail) are much darker than the rest of the body. A less marked expression of this temperature sensitive pigmentation is seen in the Burmese breed, the most common variety of which is a rich brown with very slightly darker "points" but without the blue eyes seen in the Siamese. The hybrid of Burmese and Siamese, known as a Tonkinese, has intermediate colouring (paler body merging into darker "points" with aquamarine eyes). The Siamese coat pattern is additionally seen in many other breeds, e.g. the Birman, Ragdoll, Snowshoe, and Colourpoint Persians and British Shorthairs.
not my words but gives you and idea of what I meant - am trying to get to grips with the genetic thing can you tell!!
