GENE20001 Lecture Notes - Lecture 31: Desert Sucker, Balancing Selection, Esterase
Document Summary
Environmental heterogeneity: different time and different places, different alleles are favoured by natural selection. Frequency-dependent selection: rarer a genotype it is, the fitter it is. Selective agents are always some component of the environment. The environment varies in time (temporally) and space (spatially/geographically); Therefore selection coefficients vary temporally and/or spatially (geographically), therefore. Allele frequencies will be correlated with variation in the selective agent (environmental factor) Looking at alleles a1 and a2 in a gene that produces an esterase. Found that a1 is fixed in the south. If it was we would presume that enzymes have different catalytic activity at different temp. Note a1 allele better at warm temp and a2. Note a1 allele better at warm temp and a2 is worse at warm temp. explains why a1 fixed in hot south arizona. From 10oc - 25oc there is heterozygous advantage. We need relative fitness to see if selection is operating. We have a correlation but not evidence of causation.
