anthropology notes for test2

anthropology notes for test2 - Anthropology Notes for test...

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Anthropology Notes for test 2 1. Interaction between Mutation and Natural Selection - Polymorphism = situation in which there are 2 or more alleles for a gene and at least 2 of those alleles have a frequency > 1% o In humans, 28% of genes are polymorphic o It is explained by the action of natural selection of mutation. - Balanced polymorphism = situation in which there are 2 or more alleles and at least 2 alleles have a frequency >1%. The polymorphism is due to the heterozygote having higher fitness than both homozygotes. o Example: red blood cell variations and malaria I. Sickle-cell hemoglobin A. Hb-composed of two α and two β polypeptide chains; each α chain has 141 amino acid sequences and each β chain has 146 amino acid sequences. 1) sickle-cell Hb is due to a single point mutation involving replacement of a single amino acid in the β chain. 2) in some populations, sickle-cell anemia is maintained at polymorphic levels (around 5-15%) 3) as a polymorphism, the sickle cell allele must provide a natural selective advantage. B. Malaria – caused by a parasite (transmitted by mosquitoes) C. Evidence for a relationship between sickle-cell Hb and malaria 1) geographical correlation between the incidences of polymorphic levels of sickle-cell Hb and malaria 2) clinical evidence – individuals who are heterozygous for sickle-cell have a lower rate of parasite infestation than individuals who are homozygous for normal Hb D. Why is heterozygousity for sickle-cell advantageous? 1) in malarial situations, heteros for sickle-cell show selective destruction of red- blood cells 2) uninfected red blood cells do not sickle, but rather deliver adequate O 2 into the tissues 3) red blood cells infected with the parasites do sickle, and they kill the parasite. 4) thus, heteros can conjointly suppress parasite proliferation and supply O 2 to the tissues. 5) as the heteros have the selective advantage over both homos in a malarial
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This note was uploaded on 05/04/2008 for the course ANTH 1001 taught by Professor Tague during the Spring '07 term at LSU.

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anthropology notes for test2 - Anthropology Notes for test...

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