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This lesson covers meiosis as required by AQA GCSE Biology specification 4.1.1 (Higher Tier only). You need to understand the process of meiosis, how it differs from mitosis, and why it is essential for sexual reproduction and genetic variation.
Meiosis is a type of cell division that produces gametes (sex cells). In animals, the gametes are sperm cells and egg cells (ova). In flowering plants, the gametes are pollen and egg cells.
Meiosis is sometimes called reduction division because it reduces the chromosome number from diploid (2n) to haploid (n).
| Term | Meaning | Chromosome Number (Humans) |
|---|---|---|
| Diploid (2n) | A cell with two complete sets of chromosomes (one from each parent) | 46 chromosomes (23 pairs) |
| Haploid (n) | A cell with one complete set of chromosomes | 23 chromosomes |
When two haploid gametes fuse during fertilisation, the resulting zygote is diploid again (23 + 23 = 46). This maintains the correct chromosome number from generation to generation.
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