anthropology notes for test2

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

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
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
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

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

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online