Lesson 4.2.3

4.2.3 Hardy-Weinberg and reproductive isolation Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 4

20 questions

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Lesson 4.2.3, Hardy-Weinberg and reproductive isolation: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 4: Biodiversity and Natural Resources, written with Revision Ninja.

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The 20 questions

  1. What does the Hardy-Weinberg equation p^2 + 2pq + q^2 = 1 describe?

    • The number of different alleles present at a single locus in a species
    • The rate at which new mutations arise in a gene pool
    • The proportion of individuals that survive to reproductive age
    • The expected genotype frequencies in a population that is not evolving

  2. In the Hardy-Weinberg equation, what does p represent?

    • The frequency of homozygous recessive individuals in the population
    • The frequency of the recessive allele in the population
    • The frequency of heterozygous individuals in the population
    • The frequency of the dominant allele in the population

  3. Which condition is NOT required for a population to remain in Hardy-Weinberg equilibrium?

    • Random mating between individuals in the population
    • Frequent mutation at the locus studied
    • No selection acting on the locus studied
    • No net migration into or out of the population

  4. What term describes two groups that can no longer interbreed and so no longer share genes?

    • Reproductive isolation
    • Stabilising selection
    • Directional selection
    • Genetic drift

  5. Reproductive isolation can lead to the formation of new species mainly because it:

    • stops gene flow so that different alleles accumulate in each population
    • forces every individual in both groups to become heterozygous
    • guarantees identical allele frequencies in both groups over time
    • increases the mutation rate in both populations equally

  6. Which of the following is a prezygotic isolating mechanism?

    • Hybrid offspring that are sterile and cannot reproduce
    • Hybrid adults that die before reaching reproductive age
    • Hybrid zygotes that fail to develop into viable embryos
    • Differences in mating behaviour that prevent mating

  7. If the frequency of the recessive allele q is 0.3, what is the frequency of the dominant allele p?

    • 0.7
    • 0.09
    • 0.6
    • 0.3

  8. In a population in Hardy-Weinberg equilibrium, q = 0.2. What is the expected frequency of heterozygotes (2pq)?

    • 0.32
    • 0.16
    • 0.64
    • 0.04

  9. A recessive genetic condition affects 1 in 10000 people (q^2 = 0.0001). Approximately what fraction of people are carriers (heterozygotes)?

    • About 1 in 200
    • About 1 in 50
    • About 1 in 10
    • About 1 in 100

  10. In a sample of 500 individuals, 45 show the recessive phenotype (aa). What is the frequency q of allele a?

    • 0.3
    • 0.45
    • 0.7
    • 0.09

  11. A population of 1000 has 360 AA, 480 Aa and 160 aa individuals. What is the frequency of allele A?

    • 0.36
    • 0.6
    • 0.72
    • 0.5

  12. A population is in Hardy-Weinberg equilibrium with p = 0.6 and q = 0.4. How many of 1000 individuals are expected to be heterozygous?

    • 360
    • 240
    • 600
    • 480

  13. A population shows allele frequency q = 0.2 in generation 1 and q = 0.35 in generation 10. What does this change indicate?

    • Evolution (a change in allele frequency) is occurring in the population
    • The population is at Hardy-Weinberg equilibrium
    • The mutation rate has fallen to zero in the population
    • Reproductive isolation has already produced a new species

  14. In a population of 200 with p = 0.5, what is the expected number of homozygous recessive individuals?

    • 25
    • 50
    • 150
    • 100

  15. Hybrids from two diverged populations are sterile, as with mules. Which type of isolating mechanism is this?

    • Temporal isolation
    • Geographic isolation only
    • Postzygotic isolation
    • Prezygotic isolation

  16. A recessive allele is at frequency q = 0.1 in a population. Why does selection against recessive homozygotes remove the allele only slowly while it is rare?

    • Recessive alleles are always lost after a single generation of selection
    • Heterozygotes are always selected against, so the allele is protected
    • Only mutation acts on q, so selection has no effect at all
    • Most copies of a rare recessive allele sit in heterozygotes, which selection cannot see

  17. Two isolated populations both start with q = 0.5. Independent drift and selection later leave q at 0.8 in one and 0.2 in the other. Which process most directly causes the growing difference?

    • Identical stabilising selection in both populations
    • A uniform mutation rate that removes differences between them
    • Gene flow between the two populations mixing their alleles
    • Reduced gene flow, so each population drifts separately

  18. A population has p = 0.7. Each generation, individuals with p = 0.3 migrate in and make up 10% of the breeding population. What is p after one generation of migration (ignoring other forces)?

    • 0.78
    • 0.52
    • 0.66
    • 0.70

  19. A population starts with AA 0.5, Aa 0.0 and aa 0.5, with random mating and no other forces. What are the genotype frequencies in the next generation?

    • AA 0.50, Aa 0.00, aa 0.50
    • AA 0.25, Aa 0.50, aa 0.25
    • AA 0.50, Aa 0.25, aa 0.25
    • AA 0.125, Aa 0.75, aa 0.125

  20. Which change would most increase the chance that allele frequencies shift by genetic drift?

    • Increasing the population size to 100000 individuals
    • Introducing random mating into the population
    • Ensuring there is no migration into the population
    • Reducing the population size to about 20 individuals

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