Calico cats are not a breed of cat; calico is a color pattern. To be called "calico", a cat must have black, white and orange in its coat. Variations of these colors include gray, cream and ginger. True calicos have large patches of these three colors, whereas a tortoiseshells or "torties" have a mix of these colors often blended or swirled together, rather than separate blocks of color. The size of the patches can vary from a fine speckled pattern to large areas of colour. Typically, the more white a cat has, the more solid the patches of color. In the UK, these cats are called "tortoiseshell and white". We have more photos of very cute calico kittens.
Many people are surprised to learn that most cats with this coat pattern are female. This is due to genetics. Coat color in cats is a physical characteristic related to gender. Female animals have two X chromosomes (XX), males have one X chromosome and one Y chromosome (XY). The genetic coding for black or orange coat color is found on the X chromosome. The coding for white is a completely separate gene.
Since females have two X chromosomes, they can show two colors (orange and black, or variations of these) and white; creating the 3-color calico mix. Since males have only one X chromosome, they can only be orange OR black. The complex process of dominant and non-dominant genes comes into it too, but that is the basis for coat color in these cats.
I did say that most calicos are female. They can be male in rare instances. In this case, the cat will have two X chromosomes and one Y chromosome (XXY). Cats with this chromosomal composition are usually sterile...is similar to a human condition called Klinefelter's syndrome.
Interesting fact: on October 1, 2001, the calico cat became the official cat of the state of Maryland in the United States.
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