C locus — colourpoint (Siamese)

Controls: The pointed pattern — a pale body with darker face, ears, legs and tail.

How it works

The C (albino series) locus carries a temperature-sensitive form of pigment. The recessive Siamese allele (cs) only lets colour develop in the cooler parts of the body — the 'points' (face, ears, legs, tail) — while the warm body stays pale. Point cats are ALWAYS blue-eyed. The Burmese allele (cb) gives a softer sepia; cs with cb together gives 'mink'.

Alleles

CFull colourDominant

cbBurmese (sepia)Recessive

csSiamese (point)Recessive

Breeding examples

Colourpoint (cs/cs) × Colourpoint (cs/cs)

← All kittens colourpoint, all blue-eyed.

Full colour carrying point (C/cs) × Full colour carrying point (C/cs)

← ≈ 1 in 4 colourpoint; the rest full-coloured (some carriers).

Full colour (C/C) × Colourpoint (cs/cs)

← All kittens full-coloured, and every one carries point.

Frequently asked questions

Why do colourpoint cats always have blue eyes?+

The same gene that limits pigment to the cool points also reduces pigment in the eye, which makes the eyes blue. It is a fixed part of the pointed pattern.

Why do point cats get darker with age?+

Because the pigment is temperature-sensitive, cooler skin grows darker fur. Older cats, and cats in cold climates, develop deeper points and a slightly shaded body.

Can two non-point cats have a point kitten?+

Yes — cs is recessive, so two full-colour cats that both carry it can produce a colourpoint kitten.

Related genes

W locus — dominant white

A fully white coat that masks all other colour.

O locus — orange (red)

Red/cream colouring, and tortoiseshell in females.

B locus — black series

Whether the black pigment shows as black, chocolate or cinnamon.

See these colours on real cats.

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