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Hardy Weinberg Equilibrium

Hardy Weinberg Equilibrium. p 2 +2pq+q 2 =1. The Basics. The formula is essential for population genetics. The law states that both allele and genotype frequencies in a population remain constant from generation to generation.

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Hardy Weinberg Equilibrium

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  1. Hardy Weinberg Equilibrium p2+2pq+q2=1

  2. The Basics • The formula is essential for population genetics. • The law states that both allele and genotype frequencies in a population remain constant from generation to generation. • Therefore, given observed genotype frequencies we can calculate the allele frequencies and in turn calculate the expected genotype/allele frequencies for the next generation.

  3. Example Question Last year, the bison population in Elk Island National Park was genotyped at the BMC 1222 locus. If the population remains in Hardy-Weinberg Equilibrium what is expected genotype frequencies of the next population?

  4. Solution First the allele frequencies have to be calculated using the formula: p=(2(nAA)+(nAa))/2ntotal Total population = 14+12+17 = 43 p(102) = ((2)(17)+12)/((2)(43)) p(102) = 0.5349 p(104) = ((2)(14)+12)/((2)(43)) P(104) = 0.4651

  5. Now we can compute the expected genotype frequencies using the allele frequencies of 102 and 104 in combination with p2+2pq+q2=1 You can think of p being 102 and q being 104. 102/102 is the same as p2 (0.5349)2 = 0.2861 102/104 is the same as 2pq 2(0.5349)(0.4651) = 0.2163 104/104 is the same as q2 and can be calculated using the equation: p2+2pq+q2=1 0.2861+0.2163+q2=1 1-0.2861-0.2163= q2 Therefore, q2= 0.4976

  6. More than 2 Alleles? • The Hardy-Weinberg Equilibrium is the fundamental principle of population genetics. • Therefore, it can be applied to loci of more than two alleles. • For example, if there was three alleles the equation would be modified slightly so it would have another term. Consider r being another allele frequency. p2+r2+2pq+2pr+2rq+q2=1

  7. Quick Note • Because this is a fundamental concept in population genetics there are calculators available on the web. • You will be required to calculate expected genotype and allele frequencies for loci with two alleles only. As well as converting the expected genotype frequency into the expected number of individuals.

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