Explain how meiosis produces gametes that are genetically different from each other.

AQA A-Level Biology (7402) — 3.4.3 Mutation and Meiosis · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Meiosis is a two‑stage division (meiosis I and meiosis II). In meiosis I homologous chromosome pairs separate, so each daughter cell receives one chromosome from each pair. During metaphase I the pairs align independently, giving random distribution of chromosomes (independent assortment). This means each of the four resulting cells (gametes) has a different combination of chromosomes. The cells are haploid, containing half the chromosome number of the parent. Additionally, errors in chromosome segregation or DNA replication during meiosis can introduce mutations, further increasing genetic diversity.

Examiner tips

  • Mention both stages of meiosis and the key event in each
  • Explain independent assortment as the source of different chromosome combinations
  • State that the result is four haploid gametes
  • Include that mutations can add further variation

Common mistakes

  • Confusing meiosis with mitosis or omitting the two‑stage nature
  • Failing to mention independent assortment or random distribution
  • Not stating that gametes are haploid

Mark scheme (5 marks)

  1. Meiosis involves two divisions (meiosis I and meiosis II)
  2. Homologous pairs of chromosomes separate during the first division
  3. Chromosomes are distributed/sorted randomly (independent assortment) so each gamete receives a different combination of chromosomes
  4. Four gametes are produced, each with half the chromosome number (haploid)
  5. Mutations can occur during meiosis, introducing further genetic variation into gametes

Key terms in this question

meiosis · gametes

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