Cell Division: Meiosis — AQA GCSE Biology
Meiosis is the special type of cell division that produces gametes (sex cells) for sexual reproduction.
Where and why meiosis happens
Meiosis takes place in the reproductive organs (ovaries and testes in humans). It produces gametes — sperm and egg cells in animals, pollen and egg cells in plants.
What happens in meiosis
- It produces four daughter cells from one parent cell.
- Each gamete has half the number of chromosomes (it is haploid) — in humans, 23 instead of 46.
- The four gametes are genetically different from each other and from the parent.
This halving is essential: at fertilisation, two gametes fuse, restoring the full chromosome number (diploid). The new cell then divides by mitosis to form an embryo, and cells later differentiate.
Meiosis and variation
Because the genes are shuffled and gametes are genetically different, meiosis (combined with random fertilisation) produces variation in the offspring.
Comparing mitosis and meiosis
| Mitosis | Meiosis | |
|---|---|---|
| Cells produced | 2 | 4 |
| Genetically | identical | different |
| Chromosome number | same as parent | halved |
| Purpose | growth, repair | making gametes |
Exam tips
- Meiosis makes four genetically different, haploid gametes.
- The chromosome number is halved, then restored at fertilisation.
- Meiosis introduces variation; mitosis produces identical cells.
- Remember the sequence: meiosis → gametes → fertilisation → mitosis → growth/differentiation.