Odd Eyed & Dominant Blue Eyed Sphynx

The "Dominant Blue Eye" (DBE) gene is a mutation that enables cats to inherit vivid deep blue or uniquely coloured eyes. This dominant gene shows incomplete penetrance. When a DBE carrier mates with a DBE latent or any non-DBE cat, about half the kittens may inherit DBE, potentially resulting in blue-eyed or odd-eyed offspring.

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There's also a notable chance of producing kittens with mosaic eye color, where the green or yellow eye has some blue coloring. This mosaic trait disqualifies cats from shows and isn't recommended for breeding.

Initially, two cat breeds showed dominant blue eyes due to a random mutation, and their genes are used in Sphynx Breeding Programs:

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• Altai Blue-Eyed (Russia)

• Ojos Azules (USA)

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Current breeding efforts focus on these breeds' genetics, involving many crossbreeds with other breeds like British or Maine Coon. The goal is to introduce varied eye colors while reducing white coat markings.

Each mutation, whether Altai or Ojos Azules, can have unique traits, affecting the cat's genotype and phenotype. It's important to note that DBE gene expression varies. A kitten inheriting the DBE gene might not always have blue or odd eyes. Some kittens can be DBE latent, having yellow or green eyes that may show a red glow like color-pointed cats or have glowed when young. These cats can produce DBE blue-eyed kittens.

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Heterozygotes from a DBE carrier and DBE latent or non-carrier mating can produce kittens with:

• DBE Blue eyes

• Odd eyes

• Odd eyes with sectorial coloring (mosaic eyes)

• Latent eyes

• Normal eyes (yellow, green, or blue color point)​​

All kittens inheriting the DBE gene (including latents) will have some white in their coat. This can range from large patches to tiny spots, sometimes barely visible in overlooked areas like the mouth, scrotum, or between toes. White spots often appear on the chin or lower body, sometimes extending to a medallion.

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Several known DBE mutations exist, potentially on different chromosomes and in various genes. Similar mutations occur in humans and other animals, except cats (like mice, ferrets, dogs, and horses). Human mutations became well-known through Dutch scientist, ophthalmologist, and geneticist Petrus Johannes Waardenburg, who studied and described them between 1948 and 1951.

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In recognition of this researcher, the related human traits were dubbed "Waardenburg syndrome." It's important to note that many mutations that create breeds or colors in pets are labeled as "syndromes" and "genetic disorders" in people. For instance, albinism or any change in normal human skin color is automatically seen as a disease. Conditions are linked to changes in genes like:

• ASIP (causing major metabolic issues and "yellow obesity" in humans, but creates banded fur colors in cats)

• TYR (leading to oculocutaneous albinism and higher skin cancer risk in humans, but produces color point patterns in cats)

• KIT (causing the skin condition Piebaldism and playing a role in cancer in humans, but results in white patches in cats), and so on.

Research on Ojos Azules showed that dominant blue eyes are linked to a specific form of the white spotting gene (So), which acts early in embryo growth. This gene stops pigment cells from moving to areas that close up early in the embryo, like the tail tip and eye iris.