[M.D. Holloway]

Originally Posted by VaSteve

I'm sure it's real. I had a cat like that once. It pops up quite a bit in the Tortoiseshells. They are also very smart and I have heard, almost always female.

A "true" calico cat has large blocks of these three colors, a "tortoise shell" or "tortie" cat has a mix of these three colors (blended/swirled together more than distinct blocks of color).

The coat color in cats is a sex-linked trait, a physical characteristic (coat color) related to gender. Female animals have two X chromosomes (XX), males have one X chromosome and one Y chromosome (XY). The genetic coding for displaying black or orange color is found on the X chromosome. The coding for white is a completely separate gene.

Since females have two X chromosomes, they are able to "display" two colors (orange and black, or variations thereof) and white; creating the 3-color calico mix. Since males have only one X chromosome, they can only be orange OR black. It is more complicated than simply having the color genes -- it is a complex process of dominant and non-dominate genes interacting on the X chromosomes, but that is the basis for coat color in calico cats.

Can a calico cat ever be male? Yes, in rare instances. In this situation, the cat has two X chromosomes and one Y chromosome (XXY). Cats with this chromosomal configuration are usually sterile (not able to breed). This is similar to a condition in humans called Klinefelter's syndrome, or XXY Syndrome.