Hardy-Weinberg Equilibrium Problems: Worked Examples for AP Biology

📚 Quick Study Guide

🧬
• Hardy-Weinberg Equilibrium: Describes a population where allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary influences.
🧪
• Assumptions: Large population size, random mating, no mutation, no gene flow, no natural selection.
🔢
• Equations:
  • Allele frequencies: $p + q = 1$ (where $p$ is the frequency of the dominant allele and $q$ is the frequency of the recessive allele).
  • Genotype frequencies: $p^2 + 2pq + q^2 = 1$ (where $p^2$ is the frequency of homozygous dominant genotype, $2pq$ is the frequency of heterozygous genotype, and $q^2$ is the frequency of homozygous recessive genotype).
💡
• Key Tip: Always start by calculating $q^2$ (frequency of the homozygous recessive genotype) if you can directly determine it from the problem (e.g., percentage of individuals with a recessive trait).

Practice Quiz

1. Which of the following conditions is NOT a requirement for Hardy-Weinberg equilibrium?
   1. A. Large population size
   2. B. Random mating
   3. C. Natural selection
   4. D. Mutation
2. In a population, 16% of individuals express the recessive phenotype. What is the frequency of the recessive allele?
   1. A. 0.04
   2. B. 0.16
   3. C. 0.4
   4. D. 0.84
3. If the frequency of the dominant allele is 0.6, what is the frequency of the heterozygous genotype?
   1. A. 0.16
   2. B. 0.36
   3. C. 0.48
   4. D. 0.6
4. A population of butterflies has two alleles for wing color, B (dominant, black) and b (recessive, white). If the frequency of the b allele is 0.3, what is the frequency of the BB genotype?
   1. A. 0.09
   2. B. 0.21
   3. C. 0.49
   4. D. 0.7
5. Which of the following factors can cause deviations from Hardy-Weinberg equilibrium?
   1. A. Random mating
   2. B. No mutation
   3. C. Gene flow
   4. D. Large population size
6. In a population of snails, the frequency of the homozygous recessive genotype (aa) is 0.01. What is the frequency of the dominant allele (A)?
   1. A. 0.01
   2. B. 0.1
   3. C. 0.9
   4. D. 0.99
7. If a population is in Hardy-Weinberg equilibrium and the frequency of the homozygous recessive genotype is 0.25, what is the frequency of the heterozygous genotype?
   1. A. 0.25
   2. B. 0.5
   3. C. 0.75
   4. D. 1