Cat fur color is a common teaching tool in biology and genetics classes. Figuring out which genes create the family feline’s coat color is a fun way to help students learn the basics of genetic inheritance. I want to share that fun with you, so here are the seven genes that control virtually all the common cat coat color characteristics.
The B gene controls the production of eumelanin, the pigment that makes a cat’s fur black. It comes in three alleles, or types. The B allele, which produces black fur, is dominant, meaning a cat only needs to get a B allele from one parent in order to be black. Two other recessive alleles of the B gene, b and b’, produce chocolate and cinnamon coat colors, respectively.
This gene controls the coat’s "ticking," or banding of colors on a cat’s fur. The dominant allele, A, produces banded furs which help to create the tabby pattern. The recessive allele, a, makes the cat’s fur a solid color from tip to root.
If a cat inherited the A allele, the T gene determines what kind of tabby pattern will be produced. The dominant allele, T, produces the mackerel or striped tabby coat; the Ta allele produces an all-agouti tabby like the Abyssinian; and the recessive tb allele produces the classic, or blotched, tabby.
The dominant D, or full-pigmented, allele produces cats that are black, brown, or orange. The recessive d allele produces paler colors like gray (known as blue to breeders), tan, or cream.
This gene actually can mask other coat colors, including black. Although the o, or non-orange, allele is much more common, if a cat gets the dominant O allele, any other colors will be covered up and the cat will be orange. For more information on how genes create orange cats, check out an interview my orange tabby cat, Kissy, did with a professor of biology and genetics.
The dominant S allele produces white spotting that masks the cat’s true color in the areas where the spots occur. This produces tuxedo cats, "cow kitties," and cats with white "lockets" or white boots and mittens. It even produces cats that are entirely white because their fur is just one giant white spot. The recessive s allele is actually the normal expression of this gene; it produces no white fur at all.
The W gene is known as a masking gene. That means if the dominant W allele is present, the cat will be white, no matter what the other coat color and pattern alleles say. The recessive w allele produces full expression of any of the other color traits. But how can you tell a white cat with the dominant W allele from a white cat with an S allele that created a giant white spot? A white cat with the W allele has pale blue or orange eyes, whereas a white cat that is white because of the S allele will have green or yellow eyes.
Granted, this is a lot to take in, but it’s only the beginning when it comes to genes that control what your cat looks like. The "pointing" gene gives Siamese cats their distinctive pattern, and other genes produce the smoke coloration seen in some purebred cats. Still other genes control the length of the fur, body type, ear and face shape, tail length, and much more.
If you want to know more about any aspect of cat genetics, please let me know in the comments! If there’s enough interest, I’ll write an article that goes into more depth on the subject.