Cat Genetics

Dilution

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We know that dilution means a watering down of a color. In painting this is achieved by the addition of water to color pigment so that the same amount of color pigment is spread over a wider area. What is happening to the color of a cat's coat when there is color dilution.

Perhaps a good starting point is to look at the hairs of the coat at a microscopic level in a before and after sequence. There are four basic solid (self in cat fancy language) dense colors: black, cinnamon, chocolate and red (there are some green cats too apparently). Self colored cats carry the non-agouti gene. This is a recessive gene in homozygous form (aa). This allows black pigmentation (the substance is called eumelanin) to be produced throughout the hair as it grows. This is in contrast to the agouti gene, the presence of which results in banding of color in the hair. Taking the self (solid) color of black as a good example, the genotype is aaB-D-. B stands for the browning gene, which in dominant form (signified by a capital B) produces black pigmentation. The capital letter D stands for the dominant dense pigment gene. See black cats.

When the cat coat's color shows dilution it is due to the presence of the two recessive d alleles in the place of the dominant gene D (dd -called maltese dilution after cats imported from Malta in the early years of the cat fancy). This has an affect on the production of pigment granules in the hair. The granules become enlarged and uneven. This creates a dilute appearance. Diluted black produces grey (gray) as we know and in the cat world the color is called blue as it is a blue/grey. There are some cats that are only grey. Diluted chocolate becomes lilac, cinnamon becomes fawn and red becomes cream. The eye color remains unchanged.

Dilute cat coats can be further modified by the dilute modifier gene (Dm). This could be called double dilution. This gene only affects dilute cats coats. The diluted black that became blue then takes on a brownish color and is called caramel (hence the term that this gene "caramelizes the color). Lilac becomes taupe and cream becomes apricot. Of course the color white cannot show dilution (see cat coats white).

ｒｅｄ/ｃｒｅａｍ/ａｐｒｉｃｏｔ

ｃｈｏｃｏｌａｔｅ/ｌｉｌａｃ/ｔａｕｐｅ

ｂｌａｃｋ/ｂｌｕｅ/ｃａｒａｍｅｌ

This was as close as I could get to caramel...

ｃｉｎｎａｍｏｎ/ｆａｗｎ