Explain why the daughter cells produced by meiosis are described as haploid and why this is important for fertilisation.

Edexcel GCSE Biology (1BI0) — 3.2 Meiosis · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Meiosis reduces the chromosome number by half, so each daughter cell contains only one copy of every chromosome.
This makes the cells haploid (gametes).
When fertilisation occurs, a male and a female gamete fuse and their nuclei combine.
The fusion restores the full diploid chromosome number in the fertilised egg (zygote).

Examiner tips

Use the term ‘haploid’ and explain it means one set of chromosomes.
Show the link between halving in meiosis and restoring diploidy at fertilisation.
Mention gametes (sperm/egg) to satisfy the context.

Common mistakes

Confusing diploid with haploid or vice‑versa.
Failing to state that fertilisation restores the diploid number.
Using vague language like ‘half the chromosomes’ without specifying ‘one set’.

Mark scheme (4 marks)

Meiosis produces cells with half the usual number of chromosomes / a single copy of each chromosome
This means the daughter cells are haploid (gametes)
At fertilisation, the male and female gametes fuse / their nuclei combine
This restores the full / diploid chromosome number in the fertilised egg / zygote

Key terms in this question

meiosis · fertilisation