Explain why sexual reproduction, which relies on meiosis, produces offspring with more genetic variation than asexual reproduction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Some organisms, such as strawberry plants, can reproduce both sexually and asexually. The offspring produced by each method differ in their genetic variation.
Model answer (5 marks)
1. Meiosis produces haploid gametes.
2. During meiosis, crossing‑over and independent assortment generate gametes that are genetically different from one another.
3. Fertilisation combines two different gametes, so the zygote contains a new mix of alleles from both parents.
4. In asexual reproduction, mitosis produces offspring that are genetically identical to the single parent.
5. Mutations can occur during meiosis or mitosis, but they are more likely to create new alleles in the diverse gametes of sexual reproduction, adding further variation.
2. During meiosis, crossing‑over and independent assortment generate gametes that are genetically different from one another.
3. Fertilisation combines two different gametes, so the zygote contains a new mix of alleles from both parents.
4. In asexual reproduction, mitosis produces offspring that are genetically identical to the single parent.
5. Mutations can occur during meiosis or mitosis, but they are more likely to create new alleles in the diverse gametes of sexual reproduction, adding further variation.
Examiner tips
- Use the exact terms – meiosis, gametes, fertilisation, mitosis, mutations. Show the chain: meiosis → gametes → fertilisation → zygote. Mention crossing‑over/independent assortment as sources of variation.
- Include the point about mutations as an extra source of variation in sexual reproduction.
Common mistakes
- Confusing mitosis with meiosis or vice‑versa. Failing to mention fertilisation or the role of crossing‑over. Using vague language like "different" without explaining how gametes differ.
Mark scheme (5 marks)
- Meiosis produces gametes / sex cells
- Gametes produced by meiosis are genetically different from each other (genetic variation in gametes)
- Fertilisation combines genetic material from two parents
- Asexual reproduction uses mitosis / only one parent, so offspring are genetically identical to the parent
- Mutations can introduce new alleles / new genetic variation, adding further variation in sexual reproduction
Key terms in this question
meiosis · asexual reproduction · genetic variation
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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