CHINESE CRESTED - the Lethal Gene

Coated dogs play a critical role in any breeding program when a potentially lethal gene is involved for the survival of the hairless dog. Hairlessness is due to a dominate gene. Coated offspring occur in hairless to hairless breedings and hairless to coated breedings. This is because hairlessness in dogs is dominate and not recessive as in most mutations.

Hairlessness is the result of an incomplete Dominate mutation, which is lethal when homozygous (carrying only the hairless gene). Hairlessness in dogs is dominant and not recessive as in most mutations. The hairless and powder puff varieties are inseparable due to this genetic makeup.

The unique difference with the Chinese Crested and other hairless breeds is that the Crested carries the gene for long hair; all other hairless breeds carry short coat.

Every hairless Chinese Crested carries the dominant gene for hairlessness, hair on the head, feet, and tail only, and the gene for normal coat, which is heterozygous. Hr is dominant over the recessive hr. The gene, which produces hairlessness, is an incomplete dominate lethal. The unlucky puppy that inherits a double dose of the dominant lethal will die in the uterus or soon after birth, due to abnormalities and will not survive. The puppy that inherits a double dose of the gene for coat is a homozygous powder puff carrying no hairless gene at all; this is not a lethal combination. Both varieties carry the gene for coat; this is why the powder puff cannot be bred out. The powder puff was discarded in the past and considered not important in the breeding program. Sadly, a lot of wonderful foundation stock has been lost. The coated variety plays a critical role in maintaining health, quality, and substance of the breed. The Chinese Crested can therefore be a hairless (Hr - hr) or a powder puff (hr - hr). The homozygous puppy carrying only the hairless gene (Hr - Hr) does not survive.

Another complication to breeders is the variable amount of the dominant mutation, which can show undesirable variation of hairlessness (socks, plume, crest) or hairiness on the bodies of the individual hairless dog. Hairless dogs can genetically carry varying amounts of hair on their bodies, as well as the socks, crest, and tail plume. The extent of the hairlessness or hairiness the puppies can inherit is unpredictable. Hence we distinguish hairless puppies in two groups, either being Hairy Hairless, or True Hairless (having much less hair).

The extreme hairy hairless can often be mistaken for a lightly coated powder puff. To check if the dog is genetically hairless or a powder puff; inspect the dentition. In the hairless variety the canines are conical and point forward, which is referred to as tusks. The hairless mouths can also be missing the first and second pre-molars, which can be accepted as being typical of the hairless mouth. The powder puff will have a normal canine mouth, forty-two teeth in a tight scissor bite. With careful selective breeding the dentition of the hairless dog is much improved with teeth that are better rooted, although the canines may still be conical and point forward. Charles Darwin in his theory of evolution stated that in most animals the teeth or horns have some relationship to the growth or absence of hair. For example, pigs and elephants have forward pointing tusks.