Male Calicos and Other "Impossible" Cats

As a cat lover, I have always been enthralled by the concept of "impossible" cats: cats that defy the reasoning of feline genetics. These traits, markings, and breeds are all either totally nonexistant, or exist only in cats with mutated chromosomal structure.
The Male Calico

The "red" color in cats, actually another name for an orange tabby pattern, is carried on the X chromosome, while males have only one of. Female cats, who have two X chromosomes, are likely to carry another color gene on one of them, so they are usually either non-red or show more than one pigment color. A cat displaying orange (or cream) along with another color is called a calico or tortoiseshell.

Because two X chromosomes must be present for two colors besides white to be present, a male calico cat is technically impossible. However, "male" calico cats have occurred in the past, resulting from a mutation (the feline equivalent of Klinefelter Syndrome) that causes the cat to have XXY chromosomes and male traits, rather than standard XX or XY chromosomes. When this rare mutation is present, a male calico cat can be possible-- however, despite appearances, it is not truly male and is almost always sterile.

The Red Self

Another interesting quirk in the bizarre field of feline genetics is the impossibility of breeding a cat that is solidly orange. In cat fancier's terminology, solid cats are referred to as "selfs", and identified by their solid color: while "black selfs", "blue selfs" and even "lilac selfs" are fully possible, the "red self" is technically an impossibility.

The reason for this is that the non-agouti pattern, which overrides the tabby markings, does not affect the red gene, so even cats carrying it still display full stripes. Some cat breeds, like the Abyssinian and the now-extinct breed once called the "red self" longhair, appear to have no tabby striping, but they actually simply have paler, blurrier stripes than other cat breeds.

The Blue-Eyed Black

By the current understanding of feline genetics, it is biologically impossible for a cat to have blue eyes unless it has some degree of albinism This explains why-- according to science-- all blue-eyed cats are either white or have "point markings" that define them as temperature-sensitive albinos. Siamese cats, colorpoint shorthairs, and even dark cats with black faces can have blue eyes and still fit within the realm of biology's understanding of feline genetics.

However, a feral cat was discovered in New Mexico in 1984 who was a tortoiseshell with dark blue eyes. A breeder, noticing that she should have been impossible, took in the blue-eyed cat and used her as the basis for the Ojos Azules breed, which is noted for producing blue-eyed black cats. As of 1992, only ten of them remained because the "impossible" mutation is quite difficult to breed. Any other non-white cat displaying blue eyes is likely a temperature-sensitive albino whose markings are unusually dark.

Genes in cats are a fascinating network of possibilities, probabilities, and unlikelihoods. The celebration of feline genetics, inclusive of traits that are uncommon or outright unheard-of, is a celebration of the diversity of life itself. Life is composed of intricate networks of DNA that operate according to principles that we can never fully understand or control.