anth200apr14 - its supply of oxygen, and rbcs die- leads to...

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ANTH 200 April 14, 2008 Are modern humans still evolving? Lactose intolerance: o Lactose=sugar carbohydrate in cow milk o Broken down in gut by enzyme lactase o Lactase production: controlled by a single regulatory gene, which  turns of lactase production at weaning, about 3 years old in humans o % of American whites who are genetically lactose intolerant=18% African Americans=75% Chinese=97% Thai and Vietnamese=100% Swedes=2% o Origins of domestication of milk-producing livestock=approx. 15,000  ya among pastoral people o In what regions do we historically find pastoral peoples? Sickle cell anemia Effects: sickled RBC’s clog blood vesels, living tissue does not receive 
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Unformatted text preview: its supply of oxygen, and rbcs die- leads to severe anemia, weakness Homozygous SS genotype normally lethal; mortality by age 15 when untreated A codominant gene system o 3 genotypes: AA-normal rbcs, AS- heterozygous for sickling, SS- homo for sickling o AA: normal, AS- normal except under oxygen stress or heavy workload, as at high altitudes, SS- severely anemic, enlarged spleen, early mortality without major western medical intervention Frequency of the S allele in some areas of coastal west Africa>20%. o Why hasnt natural selection eradicated the S allele? Malaria!!...
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