Human Genetics Handout Spr08

The trait is generally observed only in males because

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Unformatted text preview: ant protein, dystrophin. The trait is generally observed only in males because the males seldom live to the age of reproduction, and therefore cannot pass the allele to female offspring. Young boys who have the trait are normal for 6-7 years, following which there is rapid deterioration of the muscles, followed by death in the early teens. Frequency = 1/3,500 males. ***Hemophilia A (306700): Observed primarily in males because the low frequency of the allele makes it extremely unlikely that the homozygous female genotype can occur. Treatment requires the injection of a blood clotting factor (Factor VIII) to compensate the the dysfunctional allele. In the early 1980s commercially prepared Factor VIII was contaminated with the HIV virus bringing the disease to many hemophiliac boys in this country and in Europe. Currently the factor is produced in genetically engineered bacteria. X-LINKED DOMINANT ***Congenital Generalized Hypertrichosis (307150): The genetic basis of the werewolves and wolf men of literature and of circus side shows, CGH causes excessive facial and upper body hair that covers extensive areas of skin. Because it is an X-linked dominant, it occurs more frequently in females than in males. The mutation actually results in the reactivation of an atavistic gene (present in ancestral species) that is related to the genes of chimpanzees and other hairy primates. In females, the lower testosterone levels and the inactivation of X chromosomes creates a more patchy version of CGH. Goltz Syndrome (305600): Caused by a highly pleiotropic dominant mutation whose effects include atrophy and linear pigmentation of the skin, syndactyly, polydactyly, and mental retardation. Unlike many other X-linked traits, Goltz Syndrome is a female-specific condition because the mutation causes in utero lethality in the...
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