AP Biology: Population Genetics Modeling Practice Questions
Practice population genetics modeling with original AP Biology multiple-choice questions. Each item connects allele-frequency calculations, Hardy-Weinberg reasoning, and evolutionary forces with clear explanations.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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1. In a diploid population, the frequency of allele A is 0.7 and the frequency of allele a is 0.3. If the population is in Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes?
Explanation. The heterozygote frequency is 2pq. With p = 0.7 and q = 0.3, 2pq = 2(0.7)(0.3) = 0.42.
2. A population has genotype frequencies AA = 0.36, Aa = 0.48, and aa = 0.16. What is the frequency of allele A?
Explanation. Allele A frequency equals the AA frequency plus half the heterozygote frequency: 0.36 + 0.5(0.48) = 0.60.
3. Which condition is required for Hardy-Weinberg equilibrium?
Explanation. Hardy-Weinberg equilibrium assumes a large population, random mating, no mutation, no migration, and no natural selection for the modeled locus.
4. In a population where a recessive phenotype occurs in 9% of individuals, what is q if the locus is in Hardy-Weinberg equilibrium?
Explanation. The recessive phenotype frequency is q^2. If q^2 = 0.09, then q = 0.30.
5. A small island population loses several rare alleles after a storm leaves only a few survivors. Which evolutionary force best explains this allele-frequency change?
Explanation. Genetic drift is random allele-frequency change, and its effects are strongest in small populations or after bottlenecks.
6. A model shows that one allele becomes more common because individuals with that allele leave more surviving offspring. Which assumption of Hardy-Weinberg equilibrium is being violated?
Explanation. If genotypes differ in reproductive success, natural selection is changing allele frequencies and the no-selection assumption is violated.
7. A mainland population sends many migrants into an island population each generation. What effect can this have on the island population's allele frequencies?
Explanation. Gene flow moves alleles between populations. If migrants reproduce, their alleles can alter the receiving population's allele frequencies.
8. Why are allele-frequency models useful in AP Biology?
Explanation. Population genetics models translate genotype counts into allele frequencies, making it possible to test whether a population is changing across generations.
9. A population begins with p = 0.5 and q = 0.5. After several generations, q rises to 0.8 because homozygous recessive individuals have higher survival. What process is most directly represented?
Explanation. When survival differences favor a genotype, selection can increase the associated allele frequency across generations.
10. A student calculates p + q = 1 for a two-allele locus. What does this equation represent?
Explanation. For a locus with two alleles, their frequencies sum to 1 because every allele copy is either one allele or the other.
11. A population's observed genotype frequencies differ strongly from p^2, 2pq, and q^2 predictions. Which conclusion is most appropriate?
Explanation. A mismatch between observed and expected genotype frequencies suggests that one or more assumptions may be violated, but the cause must be investigated.
12. Which sampling plan would give the strongest estimate of allele frequency in a large natural population?
Explanation. A large, random, geographically broad sample reduces bias and better represents allele frequencies in the population.
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FAQ
What should I know for AP Biology population genetics modeling?
Know how to calculate p, q, p^2, 2pq, and q^2, and how selection, drift, mutation, migration, and nonrandom mating can change genotype or allele frequencies.
How do I recognize Hardy-Weinberg equilibrium questions?
Look for a two-allele locus, genotype or phenotype frequencies, and assumptions such as large population size, random mating, no mutation, no migration, and no selection.
Why do observed and expected genotype frequencies sometimes differ?
Differences can indicate that a model assumption is not met, such as selection, genetic drift, nonrandom mating, gene flow, mutation, sampling bias, or a combination of factors.