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Lec5b_Jan20-2010_Ernest_PopGen

Lec5b_Jan20-2010_Ernest_PopGen - ECL242_PHR242 Ernest...

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ECL242_PHR242 January 20 2010 Ernest
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Population Genetics topics Genetic diversity Effective population size Population bottlenecks & expansions Hardy-Weinberg equilibrium/disequilibrium Linkage equilibrium/disequilibrium
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What is a Population ? Term used many ways needs definition when used in ecologic/genetic context Ecological paradigm co-occur; opportunity for interaction Epidemiology population group of organisms at risk for certain disease Evolutionary paradigm Proximity and mating potential Genetic population = Group of organisms that regularly interbreed with each other …. Define “regularly”…. It depends, doesn’t it!
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Some Terms for population genetic analysis Gene frequencies Term used in population genetics for allele frequencies. Gene diversity (expected heterozygosity): Measure of genetic variation in a population. Calculated from the squared gene (= allele) frequencies Gene flow movement of genes from one population to another, causing them to become more similar. Genetic migration is the primary agent of gene flow.
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Assumption of neutrality for population genetics Much of population genetics hinges on use of loci assumed to be neutral with respect to natural selection Differences between populations = result of mutation and random genetic drift Unbiased by complicating effects of selective forces Large sections of genome might evolve in selectively neutral manner Introns, mutations at third position in codon, etc Does amount of adaptive variation correlate with amount of neutral variation?
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What is a Population ? Panmixus Subpopulations divisions within a population Clusters of individuals more likely to breed with each other than with other subpopulations Demes Metapopulations Sources and Sinks
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Hardy-Weinberg “HWE” simplifying assumptions what are they?
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Hardy-Weinberg “HWE” no genetic drift infinite population size random mating non-overlapping generations no selection no (genetic) migration simplifying assumptions
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Hardy-Weinberg “HWE” Genotype frequencies in an infinite population can be predicted from the Gene (allele) frequencies , p and q by the formula: Remember it?
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Hardy-Weinberg “HWE” genotype frequencies in an infinite population can be predicted from the gene (allele) frequencies , p and q by the formula p 2 + 2pq + q 2 = 1
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