General Cat Color Genetics

[Heidi n Q]

Generally, there is no way of knowing what, if any definite breed, most stray, rescued or adopted cats are.

The thing about cat genetics, is all of the genes for every characteristic are "out there" in various combinations. In the early years, geographical isolation kept many cat 'breeds' pure or limited in color and body conformation expression. As people became more mobile and traveled the world, all it took was for someone to become enamored of a cat (bird, dog, horse, livestock...), bring a few specimens back home with them and begin breeding them together to create a breed. Many other general breeds were simply people collecting cats with similar characteristics and selectively breeding and culling until they had a breeding population that bred true every time.

Examples of this would be ‘color breeds’ like the Siamese-type cat Bombays, Burmese, Havanas and the 'blue' cats; Russian Blue, Chartreaux, Korat and British Shorthair. All of these breeds were deliberately bred to *keep* particular traits, which in turn *eliminated* 'wild-card' traits until the cats always bred true because certain genetics were bred out of the population.

All Siamese-type cats are homozygous (matched gene pair) for the recessive (needs 2 copies to express) pointed gene (cscs). The Meezers, Blacks/Browns and the Blue cats have also been selectively bred to eliminate the agouti gene (aa). Agouti is the gene responsible for making a cat's tabby pattern readily visible. Agouti only affects *black* hair and has no effect on red hair. All red cats will show the countershading of their tabby pattern but won’t have agouti-ticked/banded hairshafts. Black-based cats can also show countershading, but it is sometimes difficult to see. Agouti was bred into the Siamese breed to create “Lynx Point” and express the tabby markings on their points. A new breed category was created to classify them, called “Colorpoint”; which includes Lynx, the Reds, Tortoiseshells and their dilute versions.

All cats carry some form of the tabby pattern genes (Classic blotched, Abyssinian ticked and Mackerel striped, broken striped and spotted) but without a dominant agouti gene they will present as a solid colored cat. Additionally, in the case of the 'blues', they have been selectively bred to be homozygous for the recessive "dense" gene (dd), which dilutes black coats to blue.

Tortoiseshell is remarkable because the cat carries both black (o) and red (O) on her pair of XX genes. Females are XX and can carry a color on each X gene. Males are XY and only carry color on the X gene. This is why male calicos are rare because they would have to be a genetic oddity of XXY. Tortie/Torbie cats with White Spotting are commonly called “calico”, especially if their markings have definite patches of black, red and white. When the black and red are ‘marbled together’ that is called Tortoiseshell.
Torties do not carry agouti. Torties who do are called Torbies. Tortoiseshell + Tabby = Torbie.

So, while there are things I can tell about a cat's genetic make-up based on its’ phenotypical appearance, there is no way to determine what, if any, breeds influenced them with complete accuracy. With Siamese points and body conformation and Persian smush-faces, it is *easy* to see what breed influenced them, both recent and long-ago, but in general it is impossible to tell because all of these genes that influence color, markings, characteristics and body type are out there in many, many, combinations. Dogs are a little easier to distinguish contributing breeds in a mutt, but cats haven't changed body-types (body, muzzle, ears, et cetera...) as distinctly as dogs have.

heidi =^..^=

An AWESOME genetics explanation website: http://home.earthlink.net/~featherland/off/white.html

[Kobster]

I think this should be a sticky!

[Najiwench]

This is awesome! I'm a big color genetics nerd, I follow a LOT of horse color genetics and am absolutely fascinated by it (and have gotten into quite a few arguments about it LOL), and have bred mice before and studied their color genetics. I've always been curious about cats but there seems to be relatively little out there as far as their color genetics (unlike horses which is pretty easy to find).

My Spice is an amazing color and her eyes really tweak my curiosity about what kind of genetics go into her. I could geek out on this all day LOL

[Heidi n Q]

Ooooh!
Would you be interested in reading this topic and maybe posting some close-up pics of Spice's fur so I can see it?
What agouti (tabby) looks like:

Offhand (from your siggie pic) she looks like a dilute tortie and possibly pointed, as well?

[Hitomi]

Spice looks like tortie Siamese mix to me.

[Najiwench]

When she was a baby, she looked REALLY pointed, but as she's gotten older the mottled color has become more apparent. We joke that she's camouflaged to our carpet (old stained nasty stuff LOL)

I made a photobucket file just for her.

SpiceCat pictures by najiwench - Photobucket


I will get a close up of the hair as soon as the kids are finished with my phone. My good camera died and the other one is with the hubby on deployment *sigh*