DSX GENETICS IN BRIEF
Originally the name "Sphynx" was attributed to hairless cats, bred on the basis of the mutation revealed in Canada. Canadian mutation is appointed to a recessive allele - hr. Specimens that are homozygous for this allele (hrhr) do not always display hairlessness in its' full expression: sometimes they have thin residual coat with a corrupted texture, that is more prominent on legs, muzzle and tail (these are so-called Points).
Russian mutation behaved in some other way. It revealed itself as early as in the first generation bred from two cats - normal and hairless. The results of such mating were quite mixed: some of heterozygous offspring had a residual curly coat at birth, which could be extremely short ("velour") or of normal length but rare, and shafts of hair were thin. These coat texture abnormalities often came together with a bald spot on the crown, resembling a monk tonsure. These kittens lost their coat as grew older - hair bulbs died on some regions or on all surface of skin (except for points). The "shedding" happened in the period from 2 months to 2 years of age.
Other heterozygous kittens were born covered with thick curly hair of normal length. Most of them stayed completely "coated" for their lifelong. Cat specialist conditionally called this variety "brush".
Among the second generation, i.e. animals born from both "shed" parents or one - of "brush" variety and another - a "shed" cat, there was one more type of kittens - completely hairless at birth. They even could have no whiskers and their elastic "large" skin was wrinkled.
However the new mutation did something more to the general appearance of animals than just a disruption the coat development. Among the offspring, especially velour-coated, there were kittens of a very specific type: with a shortened muzzle, clearly seen cheekbones and widely set up eyes, separated with a breath. These features were tightly bond to the coat development and almost never been displayed in a "brush" type specimens. The balder the kitten was the more vivid were the mutant type features... though this happened only in the kittenhood - in contrast to "velour" animals, which kept the specific mutant features in adult age.
Adult hairless at birth Don Sphynx had a wedge-head of medium length, slightly defined (not prominent) cheekbones. The only peculiarity seen in the skull of these specimens is a "cut" chin, which is typical for most of blood lines, though not required and, in fact, not desired.
Such complex mutations as hairlessness, no doubt, have effect on physiology along with morphology. In this sense, the most evident Don Sphynx feature is reduced growth (which also correlates with the coat development): hairless and sometimes "velour" animals grow noticeably slower than their "coated" siblings. In the adult age the former are virtually of the same size as the latter.
This kind of atrichosis (hairlessness) also influences the cat's behavior: it was noted that Don Sphynx very well resist emotional stress.
Inna Shustrova, Candidate to Doctor of Biology sciences
Taken from "FRIEND: for cat fanciers", # 2 (1999)
Don Sphynx at CATS-portal