ANTH 1001 : Test 2 Notes
Document Summary
Polymorphism- situation where there exists > 2 alleles for a gene, and at least 2 alleles have frequency >1: polymorphism is due to natural selection acting on genetic variation caused by mutation. Interaction between natural selection and mutation: balanced polymorphism- situation where there exists > 2 alleles for a gene, and at least 2 alleles have frequency >1&. In malarial environment heterozygotes for sickle cell have natural selective advantage over homozygotes for normal hemoglobin and sickle cell. Alleles for both normal and sickle cell hemoglobin are maintained at high frequencies; this is a balanced polymorphism. Evolution of balanced polymorphism for sickle cell: spread of slash-and-burn agriculture is related to natural selective advantage of sickle cell allele. Other rbc polymorphics and malaria: thalassemia and g-6pd deficiency - are at polymorphic levels in some pops, homozygosis for thalassemia results in early death: heterozygotes can survive, g-6-pd deficiency- individuals are phenotypically normal. Conclusion polymorphism of rbc variants and malaria: natural selection is opportunistic.
