EEB325H1 Lecture 4: EEB325 Lecture 4
9 Feb 2017
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Mutated gene disrupts water exchange and makes breathing difficult due to mucous congestion. Purifying selection acting to mutated cftr gene from population. How quickly that occurs depends on how severe the issues is (age 5 vs 40) Homozygous for this mutated gene leads to resistance to hiv, hetero means some susceptibility. Positive selection for one variant in one environment, positive selection for another variant in another environment. Looks like positive selection but as a species is actually balanced. Secretor phenotype- blood group determines proteins on surface of blood cells. Secreted in fluids, these proteins end up on or in other tissues in your body: norovirus infections- vomiting, diarrhea, abdominal pain. Long term maintenance by balancing selection is maintaining both phenotypes in population. In premodern world, loss all fitness: resistant against malaria. Sickle cell trait has evolved four times malaria all over tropics. In heterozygous state, 90% reduction in death from malaria. Hbc (protect against severe disease- 20% in ghana)
