Some people believe that calico cats are a breed, or that calico refers to a color of a cat. Since all cats are colored, calico refers to the pattern of how the coloring appears on the cat's coat.

According to a leading expert in Feline Genetics, Dr. Elizabeth A. Oltenacu of the Department of Animal Science at Cornell University:

"Early in its inception, a calico/tortie kitty is formed by a gene known as the white spotting factor. The white spotting factor effectively slows down the migration of cells across the kitten's body. One X-chromosome in every cell is switched off.

This is a random happenstance, and when a tortoiseshell kitten appears in the litter, you will see a mix of two colors of hair on the kitten.

In a calico kitten, the white spotting factor being present allows patches of cells with the same X chromosome shut-off to develop.

The results are patches of white, orange, and non-orange in the kitten. The more white in a calico, the larger the patches of white, orange and non-orange because the migration of cells in the embryo is slowed. Once the color is in patches, you can see the effect of the tabby genes in the orange patches."

Calico cats are overwhelmingly female. According to The Cat Fancier's Association Complete Cat Book; Persian calico cats have been accepted by CFA for years and calico Persians are always female and give birth to black-and-white or red and white bi-colored sons.

Genetically, two X chromosomes are needed to produce a calico coat, which is why the majority of calico cats are females. If the colors are black/orange upon the coat, then the cat is a calico cat. If the colors are blue/cream instead of the standard black/orange, then the cat is a muted calico.

Dr. Oltenacu further explains: "There's a gene on the X-chromosome that controls orange/non-orange color. One form (allele) determines orange, the other allele non-orange (usually black, but the actual color is determined by other genes on the autosomes). Neither form is dominant to the other, so a cat with one of each is a tortie.

It has to be female, as this requires 2 X-chromosomes. Sometimes an abnormal male is born XXY instead of the usual XY, so can be tortie.

Clearly, this male is the result of inaccurate separation of the chromosomes during egg or sperm formation. Usually, males are orange or non-orange, but not tortie as they have just one X-chromosome.

Now, if the cat also has the white-spotting gene (again autosomal, not on the sex chromosome). This will cause the color to be in patches, rather than the diffuse mix of orange and black in the tortie. Hence the calico."

If the majority of calico cats are female, then does this make male calicos valuable? For cat lovers, a calico cat, regardless of gender is valuable to the owner. Calico cats are quirky, independent, a tad stubborn and fun to be around.

It is clear that calico cats have captivated hearts of cat fanciers around the world. On October 1, 2001 the state of Maryland was so enamored with this delightful cat that they declared the calico cat as their official state cat.

The author wishes to acknowledge her great appreciation for Dr. Oltenacu's assistance in preparing this article.

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