Colorpoint Patterns

The I gene is not the only gene to restrict color. Restriction of color to the extremities is called pointing.

Pointed cats are light on their bodies and darker on their "points", namely their ears, feet, tail, and nose. In male cats, hair is also darker on the scrotum.

A heat-sensitive enzyme in the melanocytes, the pigmenting cells in the cat's skin, controls this pattern.

Normal body temperature inhibits pigment production over most of the cat's body, but the enzyme is activated and hair pigmented at the points where skin temperature is lower.

Pointing can occur in any color or pattern. Because it is temperature-sensitive, kittens are born white, cats in cool countries have darker coats than those in warm parts of the world, and all cats' bodies darken markedly with age.

The clearest form is the Siamese pattern: an almost-white body and dark points, called "pointed" in this chapter.

The Burmese pattern, usually called "sepia", shows so little difference between body and points that some do not regard it as pointed.

Tonkinese  or "mink" pointing is a hybrid of Siamese and Burmese pointing. Neither gene dominates, and Tonkinese can produce mink, sepia, and pointed kittens.