Lesson 3.7.2.1

3.7.2.1 Allele frequency in populations Quiz: AQA Biology, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.7.2.1, Allele frequency in populations: 20 multiple choice questions for the AQA Biology (7402), Unit 7: Genetics, populations, evolution and ecosystems, written with Revision Ninja.

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The 20 questions

  1. What term describes the total set of alleles of all genes in a population?

    • Gene library
    • Genotype
    • Genome
    • Gene pool

  2. Which equation is the Hardy-Weinberg equation?

    • p^2 + q^2 = 2pq
    • p^2 + 2pq + q^2 = 1
    • pq = 1 minus p
    • p + q = 2

  3. In the Hardy-Weinberg model, what does the letter p represent?

    • Dominant allele frequency
    • Heterozygous genotype frequency
    • Recessive allele frequency
    • Homozygous genotype frequency

  4. What does the Hardy-Weinberg principle predict about allele frequencies over generations?

    • Remain constant
    • Increase steadily
    • Decrease steadily
    • Fluctuate randomly

  5. Which factor disrupts Hardy-Weinberg equilibrium?

    • No mutation
    • Directional selection
    • Random mating
    • Large population size

  6. What best defines a biological population?

    • All living organisms
    • Interbreeding same species
    • Non-interbreeding groups
    • Different species together

  7. In the Hardy-Weinberg equation, what does q squared represent?

    • Recessive allele frequency
    • Dominant phenotype frequency
    • Heterozygous frequency
    • Homozygous recessive frequency

  8. The frequency of the recessive phenotype in a population is 0.04. What is the frequency of heterozygous carriers?

    • 0.32
    • 0.08
    • 0.16
    • 0.64

  9. If q = 0.3, what is the frequency of the dominant allele p?

    • 0.7
    • 0.9
    • 0.09
    • 0.3

  10. In a population of 1000 individuals, 250 show the recessive phenotype. How many are expected to be heterozygous carriers?

    • 500
    • 375
    • 250
    • 125

  11. If p = 0.6, what is the expected frequency of the homozygous dominant genotype?

    • 0.16
    • 0.36
    • 0.24
    • 0.60

  12. If q = 0.1, what is the expected frequency of heterozygotes?

    • 0.01
    • 0.81
    • 0.18
    • 0.09

  13. Among 200 individuals, 32 show the recessive phenotype. What is the value of q?

    • 0.6
    • 0.32
    • 0.4
    • 0.16

  14. What causes random changes in allele frequencies in small populations?

    • Directional selection
    • Natural selection
    • Genetic drift
    • Stabilising selection

  15. How does a survival advantage for a dominant allele affect Hardy-Weinberg equilibrium?

    • Causes disequilibrium
    • Increases population size
    • Maintains equilibrium
    • Prevents mutation

  16. What effect does strongly non-random mating have on Hardy-Weinberg predictions?

    • Prevents mutation entirely
    • Alters genotype frequencies
    • Stabilises population size
    • Alters allele frequencies

  17. In a population with p = 0.7 and q = 0.3, what proportion of the dominant phenotype are heterozygotes?

    • 0.30
    • 0.46
    • 0.49
    • 0.42

  18. Two random carriers of a recessive condition have a child. What is the probability that the child is affected?

    • 1/4
    • 1/2
    • 1/16
    • 1/10

  19. A recessive condition has q = 0.01 in a population of 50 000 people. How many carriers are expected?

    • 990
    • 50
    • 1980
    • 100

  20. What process most likely explains a rapid rise in a dominant allele frequency in a large population?

    • Random sampling
    • Natural selection
    • Founder effect
    • Genetic drift

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