Odd-eyed cats

An odd-eyed cat is a cat with one blue eye and one eye either green, yellow, or brown. This is a feline form of complete heterochromia, a condition that occurs in some other animals. The condition most commonly affects white-colored cats, but may be found in a cat of any color, provided that it possesses the white spotting gene.

The odd-eyed coloring is caused when either the epistatic (dominant) white gene (which masks any other color genes and turns a cat completely white) or the white spotting gene (which is the gene responsible for bicolor and tuxedo cats) prevents melanin (pigment) granules from reaching one eye during development, resulting in a cat with one blue eye and one green, yellow, or brown eye. The condition only rarely occurs in cats that lack both the dominant white and the white spotting gene.

As with some newborn mammals, all cats are blue-eyed as kittens, and may change as the newborn ages. The differences in an odd-eyed kitten's eye color might not be noticeable, save upon close inspection. Odd-eyed kittens have a different shade of blue in each eye. The color of the odd eye changes over a period of months–for example, from blue to green to yellow or from green to blue to yellow–until it reaches its final, adult color.

Odd-eyed cats are popular within several breeds, including Turkish Van, Turkish Angora, Sphynx, Persian, Oriental Shorthair, Japanese Bobtail and Khao Manee. In 1817, the government of Turkey, in conjunction with the Ankara Zoo, began a meticulous breeding program to preserve and protect pure white Turkish Angora cats with blue and amber eyes, a program that continues today, as they are considered a national treasure. The zoo specifically prized the odd-eyed Angoras who had one blue eye and one amber eye, as the Turkish folklore suggests that "the eyes must be as green as the lake and as blue as the sky." The mascot of the 2010 FIBA World Championship, hosted by Turkey, was an anthropomorphized odd-eyed Van Cat named "Bascat".

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