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Explore the unit of evolution, the individual or the population, in population genetics. Learn about the Hardy-Weinberg theorem, genetic drift, founder's effect, gene flow, and more.
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Question? • Is the unit of evolution the individual or the population?
Example Calculation • Let’s look at a population where: • A = red flowers • a = white flowers
Starting Population • N = 500 • Red = 480 (320 AA+ 160 Aa) • White = 20 • Total Genes = 2 x 500 = 1000
Dominant Allele • A = (320 x 2) + (160 x 1) = 800 = 800/1000 A = 80%
Recessive Allele • a = (160 x 1) + (20 x 2) = 200/1000 = .20 a = 20%
A and a in HW equation • Cross: Aa X Aa • Result = AA + 2Aa + aa • Remember: A = p, a = q
Substitute the values for A and a • p2 + 2pq + q2 = 1 (.8)2 + 2(.8)(.2) + (.2)2 = 1 .64 + .32 + .04 = 1
Dominant Allele • A = p2 + pq = .64 + .16 = .80 = 80%
Recessive Allele • a = pq + q2 = .16 + .04 = .20 = 20%
Practice Problem • A fruit fly population has a gene with two alleles A1 & A2. 70% of the gametes produced in the population carry A1. What is the proportion of the population that are heterozygous?
Practice Problem • In a H-W population with two alleles, A & a, that are in equilibrium, the frequency of allele a is 0.7. What is the percentage of the population that is heterozygous for this allele?
AP Problems Using Hardy-Weinberg • Solve for q2 (% of total). • Solve for q (equation). • Solve for p (1- q). • H-W is always on the national AP Bio exam (but no calculators are allowed).
