Point (coat color)
Point coloration refers to animal coat coloration with a pale body and relatively darker extremities, i.e. the face, ears, feet, tail, and (in males) scrotum. It is most recognized as the coloration of
Siamese and other breeds of
cat, but can be found in rabbits as well.
Point coloration is a form of partial
albinism resulting from a
mutation in
tyrosinase, an enzyme involved in
melanin production. The mutated enzyme is heat-sensitive; it fails to work at normal body temperatures, but becomes active in cooler areas of the skin.
As a result, dark pigment is limited to the coldest areas of the body, that is, the extremities. Pointed
kittens are born white, since there is little temperature difference in the womb. As the kitten ages, the cooler areas darken while warmer areas remain cream to white in color. Points are not limited to solid colors or dark colors. It is possible to have a red (orange color) or fawn (pale warm gray) point. It is also possible to have a
tortoiseshell or
tabby point. If the points are not black or at least very dark, the coloration is called
colorpoints.
Because of this restriction of pigment, pointed cat's eyes are always some shade of blue, because the top layer of the iris is not covered in another color, letting the blue show through. The back of the eye also lacks pigment, giving these cat's pupils an eerie red reflection in the dark, unlike a normally pigmented cat's green to blue shine.
The point
gene is carried on the C
locus, where pure
albinism is also carried. It is shown with the sign
cs, and needs two alleles of cs for the points to be expressed. The point gene is recessive to the
tabby gene. Also carried on the C locus is the gene for the
sepia pattern. This is the darkest of all of the pigment restricting patterns, and pigment is only paled at the warmest point in the body, the abdomen. This pattern's gene is represented by
cb. When a cat carries the genes cs and cb, the
mink pattern is formed, in which the pigment distribution is between a sepia and a point cat.
These breeds either include points in the breed standard, or often contain the coloration:
*
American Bobtail*
American Curl*
Balinese*
Birman *
Colorpoint Shorthair*
Cornish Rex*
Devon Rex*
Exotic cat*
Himalayan*
Javanese*
Oriental Shorthair*
Ragdoll*
Selkirk Rex*
Siamese*
Siberian*
Californian*
Himalayan
