Population Genetics

Balance between selection and mutation on allele

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Unformatted text preview: Balance Between Selection and Mutation on Allele Frequencies Which of the following most closely approximates the equilibrium allele frequency of a lethal recessive allele, a , with an average mutation rate of 10-6 ? a) 10-6 b) 10-3 c) 2q/ u d) sq 2 e) q 3 /N Q for XLR If an X-linked lethal disorder occurs in 1/10,000 males, which of the following best approximates the expected allele frequency? A) 1/10-3 B) 1/10-2 C) 0.005 D) q E) q/N http:www.dadamo.com/wiki/wiki.pl/Bering_Straits_Bottleneck The Mitochondrial Clock Effects of Migration on Population Allele Frequencies Let m=proportion of recipient population made up of migrants from the donor population, and let P=allele frequency in donor population, and let p= original allele frequency in recipient population, then, p t+1 = (1-m)p t +mP = p t +m(P-p t ), so Δ p = p t+1-p t = m(P-p t ) Effects of Migration on Population Allele Frequencies Let M=sum of single-generation migration rates over several generations, and let P=allele frequency in donor population, and let p= original allele frequency in recipient population, then, Δ p total = M(P-p ) , so Μ=Δ p total /P-p Effects of Migration on Population Allele Frequencies The Duffy blood group (Fy a) is absent in African blacks but is found in 42% of Georgia whites and in 4.6% of Georgia blacks. Based on these data, which of the following most closely approximates the proportion of genes introduced by whites into the black population? a) 90% b) 84% c) 46% d) 22% e) 11% Effects of Migration on Population Allele Frequencies The Duffy blood group (Fy a) is absent in African blacks but is found in 42% of Georgia whites and in 4.6% of Georgia blacks. Based on these data, which of the following most closely approximates the proportion of genes introduced by whites into the black population? Δ p total = M(P-p ) , so Μ=Δ p total /P-p = 0.046 / 0.42-0 = 0.1095 Human Population Substructure • Subpopulations within major groups – non-random mating may occur • e.g., population migration, immigration – geographic isolation – genetic isolation • genetic drift • inbreeding • founder effects Some Determinants of Population Substructure • # subpopulations • allele frequencies within each subpopulation • degree of genetic isolation • correlation between alleles Linguistic Isolation Indigenous Mexico Relatedness and Inbreeding • Coefficient of Relationship R = proportion of alleles shared by two individuals sharing common ancestry • Coefficient of Inbreeding F = proportion of homozygosity across all loci in one individual resulting from related ancestors F=1/2(R) Relatedness and Inbreeding Relationship Example R F (of offspring) 1 st degree parent-child ½ ¼ 2 nd degree aunt-nephew ¼ 1/8 3 rd degree first cousin 1/8 1/16 Effect of Mating of Close Relatives on Homozygosity • Consider the chance of a/a in child of brother-sister mating • =(2pq+2pq)x ½ x ½ x ¼ = pq/4 • If q is small, p approaches 1, then pq/4= q/4 • Prob 1 or other Gp is A/a 2pq + 2pq...
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Balance Between Selection and Mutation on Allele...

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