Siamese Cat Breed

The Siamese is one of the first distinctly recognized breeds of Oriental cat. The exact origins of the breed are unknown, but it is believed to be from Southeast Asia, and is said to be descended from the sacred temple cats of Siam (now Thailand). In Thailand, where they are one of several native breeds, they are called Wichien-maat , a name meaning "Moon diamond"). In the twentieth century the cats became one of the most popular breeds in Europe and North America.
All Siamese have a creamy base coat with colored points on their snouts, ears, paws and lower legs, tails and (in males) scrota. The pointed pattern 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. This results in dark coloration in the coolest parts of the cat's body, including the extremities and the face, which is cooled by the passage of air through the sinuses. All Siamese kittens, although pure cream or white at birth, develop visible points in the first few months of life in colder parts of their body. By the time a kitten is four weeks old the points should be clearly distinguishable enough to recognize which color they are. Siamese cats tend to darken with age, and generally adult Siamese living in warm climates have lighter coats than those in cool climates.
Originally the vast majority of Siamese had seal (extremely dark brown, almost black) points, but occasionally Siamese were born with blue (a cool grey) points, genetically a dilution of seal point; chocolate (lighter brown) points, a genetic variation of seal point; or lilac (pale warm gray) points, genetically a diluted chocolate. These colors were at first considered "inferior" seal points, and were not qualified for showing or breeding. All of these shades were eventually accepted by the breed associations, and became more common through breeding programmes specifically aimed at producing these colors. Later, outcrosses with other breeds developed Siamese-mix cats with points in other cat colors and patterns including red point, lynx (tabby) point, and tortoise-shell ("tortie") point. In the United Kingdom, all pointed Siamese-style cats are considered to be part of the Siamese breed. In the United States, the major cat registry, the Cat Fanciers' Association, considers only the four original colorations as Siamese: seal point, blue point, chocolate point, and lilac point. Oriental cats with color points in colors or patterns aside from these four are considered Colourpoint Shorthairs in the American cat fancy.

Siamese have almond-shaped, bright blue eyes and short, flat-lying coats. Many Siamese cats from Thailand had a kink in their tails but over the years this trait has been considered to be a flaw and breeders have largely eradicated it, although it persists among street cats in Thailand. Many early Siamese were cross-eyed to compensate for the abnormal uncrossed wiring of the optic chiasm, which is produced by the same albino allele that produces colored points. Like the kinked tails, the crossed eyes have been seen as a fault and through selective breeding, the trait is far less common today.

Article courtesy of Wikipedia