Calico cats are always eye-catching. No matter whether their markings are big and bold or small and intermingled, cats with the calico coat pattern are always unique individuals that demand attention when they walk into a room.
Calico is not a Breed
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Many different cat breeds exist -- and calico isn’t one of them. Rather, the calico cat has a coat pattern that can be present in any breed that has the black and orange coloration. It can also be present in the absence of any pure breeding, so regardless of any pure or mixed breeding, a cat can have a calico coat.
Calico Kitten Genetics
The odds are much better for a female to be a calico than for a male. Female cats have two X chromosomes, inheriting one from each parent. Males have only one X chromosome, inherited from their mothers. X chromosomes carry the coat color gene. Some female cats will have one X chromosome carrying the gene for orange coloration and one X chromosome that carries the gene for black. A process called lyonization turns off one gene or the other in each cell, leading to a mosaic expression, according to University of Miami. Because calico cats must have two X chromosomes, the rare male calico actually has three sex-related chromosomes--two Xs and one Y. This rare condition is called Klinefelter's syndrome, but these poor kitties also have other genetic issues to contend with, too.
Calico vs. Tortoiseshell
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Calico and tortoiseshell cats are essentially the same under the skin. The major difference between the two is that the calico cat also carries the piebald gene, which produces large patches of white that hides the orange and black coloration. Calico cats will sometimes have larger patches than tortoiseshell cats, but it’s not known exactly why. One theory is that the lyonization starts earlier in a kitten’s development inside the womb, allowing larger portions of his body to become one color or the other.
Different Calico Colors
Calico and tortoiseshell cats actually come in two different colors: black and dark orange, and “blue” (gray) and “cream” (light orange). Cats showing the darker calico color are simply referred to as calico or tortoiseshell cats, while those displaying the lighter colors are called dilute calicos or, in the case of tortoiseshells, blue-creams. Dilute calicos can only be born if both parents express or carry the lighter colors. The process that produces a dilute calico is similar to that which produces a human child with blond hair: both parents must pass on the genes for that hair color, even if one or both of them have dark hair.
Patterns and Calico Cats
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The calico coat pattern can be influenced by any number of genes, called modifiers. Two of these modifiers include the smoke and cameo genes, which create a white or cream undercoat. Smokes and cameos both look normal until you ruffle the coat against the grain: then it will seem as if the calico coat has been placed on top of a white cat’s body. Alternately, other patterns can be affected by the calico pattern. Some tabby cats, called torbies, can have random blotches of the calico pattern showing in their coats. Any calico cat, however, will show tabby markings in their orange patches, because there is no true red or orange cat that is not a tabby.