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Human Genetics Handout Spr08

Although it was once believed that joseph merrick the

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Unformatted text preview: rths. Although it was once believed that Joseph Merrick, the man portrayed in the movie "The Elephant Man," had this genetic defect, strong arguments have recently been made that he was affected by the related disorder, Proteus Syndrome. Polydactyly (174200): Six fingers and six toes; this form of polydactyly is 10 times more prevalent in blacks than whites. There is another gene (an autosomal recessive) which results in six fingers and toes, but is associated with dwarfism (Ellis-Van Creveld Syndrome). Syndactyly (186100): Webbed fingers, usually between the ring and little fingers. This trait shows variable expressivity, with the amount of webbing variable. AUTOSOMAL CODOMINANT ***A, B, AB, O (110300) and M, N, MN (111300) Blood Groups: Both of these red blood cell surface antigen systems have codominant alleles. The codominant phenotypes are type AB and type MN. X-LINKED RECESSIVE Agammaglobulinemia, Swiss Type (300400): Also called X-linked severe combined immunodeficiency or the bubble-boy disease. In this X-linked recessive abnormality, the homozygous individual cannot produce the gamma chain of interleukin-2 which is essential for the growth and differentiation of T cells, B cells, killer cells, and glioma cells - all critical components of the immune system. Without this defense mechanism, persons with this disease can live their lives only in a germ free environment like a clear plastic tent; thus the term "bubble child." ***Color Blindness (303900): About 8% of boys born in the United States are red-green color blind; about 0.6% of girls born in the U.S. have the same abnormality. This is a classic example of an X-linked recessive condition occurring more often in males than in females. ***Duchenne Muscular Dystrophy (310200): The most common form of muscular dystrophy, this trait is characterized by a progressive loss of coordination due to the lack of an import...
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