No hair in the hairless dogs (except naked American terrier - american hairless terrier) is the result of an incomplete dominant mutation that is lethal in homozygot.Dr. O'Brien team found the gene 'nagości'u chinese crested in chromosome 17 on the occasion of research on neurological disease called. PNA (PNA - Progressive Neuronal Abiotrophy) (Source p.41) The name comes from the Latin lethal letalis - śmiertelny.Letalnymi called genes or genotypes, which results in the inability to life and death of the individual prior to the maturity. Lethal genes arise from mutations (gene or chromosome) that prevent the normal development of a carrier as a result of his lack of ability to syntezyjednego or more of the essential enzymes. When it can be said that the gene is lethal? Some genes affect the phenotype of the dog, reducing its chances of survival. Genes may interact and cause death shortly after fertilization. Others may prevent further development at the stage of blasts (microscopic balls of cells). Yet others may not appear until the embryo is not formed in full .. Many lethal genes causes death shortly after birth because they prevent the normal functioning of the lungs, kidneys and heart.
Each naked crested carries the dominant lethal gene 'no hair' (Hr) and the gene 'normal type of hair'(hr). Gene (Hr) is dominant over the gene (hr) in the formhomozygotes (hrhr) causes the death of the fetus. Genotype naked dog is as follows: (hrhr).
Puppies honozygotyczne in terms of gene 'no hair' (Hr) with genotype (hrhr) are not born. Die in the womb and are reabsorbed by the body.
Poowder puffy have nudity gene (Hr), only a few genes are 'normal hair' (hr), the genotype is as follows: (hrhr). Such a combination is in no way is lethal.