Explain why it is important that sperm cells are produced by meiosis rather than mitosis.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. Meiosis reduces the chromosome number from diploid (46) to haploid (23) in sperm.
2. At fertilisation the sperm’s 23 chromosomes combine with the egg’s 23 to restore the normal diploid set of 46.
3. If sperm were produced by mitosis they would remain diploid, so each fertilisation would double the chromosome number, leading to infertility or miscarriage.
4. Meiosis also creates genetic variation in sperm through crossing‑over and independent assortment, which is essential for evolution and diversity.
2. At fertilisation the sperm’s 23 chromosomes combine with the egg’s 23 to restore the normal diploid set of 46.
3. If sperm were produced by mitosis they would remain diploid, so each fertilisation would double the chromosome number, leading to infertility or miscarriage.
4. Meiosis also creates genetic variation in sperm through crossing‑over and independent assortment, which is essential for evolution and diversity.
Examiner tips
- Use the exact terms haploid, diploid, fertilisation; link meiosis to chromosome number and variation.
- Show the logical consequence of diploid sperm – chromosome doubling – to justify why meiosis is required.
Common mistakes
- Confusing mitosis with meiosis; writing that mitosis also reduces chromosome number.
- Omitting the point about genetic variation or mis‑labeling it as a side effect rather than a key benefit.
Mark scheme (4 marks)
- Meiosis produces cells with half the normal chromosome number (haploid / 23 chromosomes in humans)
- When sperm fuses with an egg at fertilisation, the correct/full chromosome number (diploid / 46) is restored
- If mitosis were used, sperm would be diploid, so fertilisation would double the chromosome number each generation
- Meiosis also produces genetic variation in the sperm cells (through shuffling of chromosomes / independent assortment)
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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