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AS & A Level · AS/A Level

Biology

Inheritance and population genetics

Name: ____________________Date: October 10, 2026
  1. 1.

    Distinguish genotype and phenotype, explaining why a dominant phenotype need not reveal a unique genotype.

    [3 marks] · no calculator
  2. 2.

    Explain how independent assortment during meiosis increases variation, specifying the condition under which two genes can be treated as assorting independently.

    [3 marks] · no calculator
  3. 3.

    For AaBb x AaBb with complete dominance and independent assortment, calculate the probability of aabb and the expected number among 320 offspring.

    [3 marks]
  4. 4.

    In a Hardy-Weinberg population, the frequency of recessive homozygotes is 0.09. Calculate recessive allele frequency and heterozygote frequency.

    [3 marks]
  5. 5.

    A small island population loses an allele after a storm, although survivors show no trait-dependent survival difference. Compare genetic drift with natural selection as explanations.

    [4 marks] · no calculator
  6. 6.

    A carrier mother and unaffected father have children for an X-linked recessive trait. Calculate the affected probability among sons and among all children, assuming equal sex probability; explain why the father's normal X does not protect sons.

    [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.

Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.