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Siamese and Himalayan coat color – explained (click here)

(I updated this and added some pictures on 7-17-12)

The term “Siamese” is often misunderstood.  When I use the term, I am referring to the COLOR, not the “breed.”  Below is an explanation of the siamese color …..

http://www.cat-world.com.au/siamese-cat-genetics

Siamese Cat Color Genetics

Cats have 19 pairs of chromosomes. Chromosomes are located in the nucleus of each cell, chromosomes make up the blueprint of animals. The chromosomes are made up of genes. Genes come in pairs, one from each parent.   Each gene is responsible for a single feature, or a group of features. One pair of chromosomes determines the cat’s sex. A female has two X chromosomes, and a male will have one X & one Y chromosome.

” *Siamese colored” cats carry a gene known as the Himalayan gene. This gene is seen in other species, such as the rabbit & the mouse. It is a mutation at the C locus & it causes partial albinism. This gene is recessive to the full colour C gene.  This means you need two doses of it (homozygous) for the Siamese colour to show up. If you mate a Siamese to a Siamese, you will get 100%  *Siamese (colored) offspring. If you mate a  *Siamese to a black cat, you will get black offspring which will carry one dose of the Siamese (cs) gene at the C locus.

This gene is heat sensitive, the cooler the area, the darker the colour. Which explains why a *Siamese has dark extremities such as the face, tail & legs. The body being the warmest part of the cat remains lighter in color. You will notice your *Siamese gets darker in the winter months, especially if your Siamese is an indoor/outdoor cat.  Siamese cats are white at birth, this is due to being in the constant warmth of the mothers womb. This coloring varies from Siamese to Siamese.

Also, if you have your cat shaved in the summer, the body cools down, and the new hair grows in dark.  As the hair grows in, the body warms up again, and the hair growth again turns light.

Genetically, a seal point Siamese is a black  cat.  But the Himalayan gene inhibits the full expression of the pigment.

The albino allele has another effect on the Siamese cat.  Strabismus (crossed eyes) is sometimes seen in the Siamese (colored) cat.  This is thought to be due to a misrouting of the nerve fibres from the eye to the brain.  Instead of the fibres splitting left & right, they criss-cross, this is believed to be contributory to strabismus.   This condition is not only seen in Siamese cats, but other species of true albino animals.  Breeders have worked hard to breed this problem out of Siamese cats.

Siamese (colored) cats come in various colours.  These colors are most seen in the “points” of the cats (face, ears, tail) – therefore they are referred to as “COLOR POINTS.”    The points can be dark brown, blue grey, pale to dark orange, or tortie (a splash of various colors).

Seal Point / Chocolate Point

Blue Point / Lilac Point (these cats ALSO have an additional gene that dilutes the brown/black to even lighter, making the color appear grey or bluish or “lilac” ….)

Cream Point / Flame Point (Cream point is a  pale version of flame, and there are varying degrees of this ….)

Tortie (a/k/a Tortieshell) Point (and also what I call “Calico Point” – when the color patterns are more distinct)

Lynx (tabby stripes) point

and here is a COMBINATION!  Lynx combined with tortie – giving the cat  some orange mixed in with the tabby areas…..

another COMBINATION – blue “tortie” point -

 

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