Point Coloration in Cats
Point coloration in cats is a form of partial albinism resulting from a mutation in tyrosinase, an enzyme involved with 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 the womb is uniformly warm. 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. This coloration is also sometimes 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 cats' 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. 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.
Read more about this topic: Point Coloration
Famous quotes containing the words point, coloration and/or cats:
“When we are in love, the sentiment is too great to be contained whole within us; it radiates out to our beloved, finds in her a surface which stops it, forces it to return to its point of departure, and it is this rebound of our own tenderness which we call the other’s affection and which charms us more than when it first went out because we do not see that it comes from us.”
—Marcel Proust (1871–1922)
“This great kindness pervades Chekhov’s literary work, but it is not a matter of program or of literary message with him, but simply the natural coloration of his talent.”
—Vladimir Nabokov (1899–1977)
“Sometimes they are little cats mewing and scratching
at the door, sometimes they are her grandmother’s voice,
and sometimes they are gigantic men of light whispering
to her to get up, to get up, to get up.”
—Joy Harjo (b. 1951)