A student states: 'Meiosis must involve two divisions because a single division is not enough to produce haploid gametes that are genetically different from one another.' Explain why the student's statement is correct.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Meiosis starts from a diploid cell that contains two copies of each chromosome.
The process must reduce the chromosome number by half, so two successive divisions are required – meiosis I and meiosis II – to produce haploid cells.
During meiosis I the homologous chromosomes are separated; because each chromosome can be positioned on either pole independently, this creates random (independent) assortment and therefore genetic variation.
Meiosis II separates the sister chromatids, giving a total of four haploid daughter cells that are genetically distinct from one another.
The process must reduce the chromosome number by half, so two successive divisions are required – meiosis I and meiosis II – to produce haploid cells.
During meiosis I the homologous chromosomes are separated; because each chromosome can be positioned on either pole independently, this creates random (independent) assortment and therefore genetic variation.
Meiosis II separates the sister chromatids, giving a total of four haploid daughter cells that are genetically distinct from one another.
Examiner tips
- Show the two stages (I and II) and explain the purpose of each
- Mention diploid → haploid reduction and independent assortment
- Use the words ‘genetically different’ and ‘four haploid cells’
Common mistakes
- Confusing meiosis with mitosis or omitting the two‑division requirement
- Failing to state that the parent cell is diploid
- Not explaining independent assortment as a source of variation
Mark scheme (4 marks)
- Meiosis starts with a diploid cell (containing two copies of each chromosome) / the parent cell is diploid
- Two divisions are needed to reduce the chromosome number from diploid to haploid (half the number of chromosomes) in the daughter cells
- The first division separates homologous chromosomes, and chromosomes can be arranged randomly / independently assorted, producing genetic variation
- This results in four genetically different haploid daughter cells (gametes)
Key terms in this question
Related
- All Edexcel GCSE Biology (1BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Meiosis questions
- Describe what happens during meiosis to produce gametes from a diploid cell.
- A diploid cell in a human testis undergoes meiosis. Explain why the four daughte…
- Explain why the daughter cells produced by meiosis are described as haploid and …
- Explain why meiosis is important for producing genetic variation in a species.