Lect_7_Genetic_Variation

2 20100 02 100 frequencies in populaon

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Unformatted text preview: s = q p + q = 1 Expected genotype frequencies: AA Aa aa P2 2pq q2 Assump'ons of the Hardy- Weinberg equilibrium - Very large popula%on size. - Random ma%ng. - No selec%on. - No migra%on. - No muta%on. ***If these condi%ons are met, allele and genotype frequencies will remain constant from genera%on to genera%on.*** Life cycle… “Punne4 square” A (p) a (q) AA (__) A (p) Aa (__) a (q) Aa (__) aa (__) How H- W equilibrium can be violated (detec%on of evolu%onary change) “Punne4 square” A (p) a (q) AA (p2) A (p) Aa (__) a (q) Aa (__) aa (q2) “Punne4 square” A (p) a (q) AA (p2) A (p) Aa (pq) a (q) Aa (pq) aa (q2) That is equivalent to the binomial expansion: (p + q )2 = p2 + 2pq + q2 For three alleles at a locus: (p + q + r)2 = p2 + q2 + r2 + 2pq + 2pr + 2qr Calcula%ng allele frequencies (p and q) using genotypic frequencies: AA Aa aa p2 2pq q2 Frequency of A = p2 + (2pq)/2 = p2 + pq Replacing q by (1-...
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