GENE20001 Lecture Notes - Lecture 32: Balancing Selection, Epithelium, Mutation Rate
Document Summary
Malarial parasites live within rbcs, intracellular invasion - ookinete gliding on epithelial cell membrane. Hypothesis: hbahbs individuals more resistant to malaria than hbahba. In the absence of malaria, fitness of hbahba>hbahbs>>hbshbs. In the presence of malaria, fitness of hbahbs>hbahba>>hbshbs. If mutation were operating you"d need a massively high mutation rate. There should be some other factor explaining the high allele frequency. Thus this is a case of balancing selection. Haemoglobin s tends to crystallise at low o2 pressure which leads to lysis of rbc. Heterozygote advantage is a candidate explanation for many of the polymorphisms observed in populations of all organisms. A protocol for demonstrating selection at a single loci. E. g. dieldrin resistiance in sheep blowfly (lucilia cuprina) Allele frequencies must be described over time in one population or through space across populations. We look for correlation between allele frequencies and some environmental variable. This is not proof this causes selection but it gives an indication.
