17.3 Meiosis

Meiosis as the nuclear division involved in the production of gametes. Meiosis described as a reduction division — the chromosome number is halved from diploid (2n) to haploid (n), resulting in genetically different cells (details of the stages not required). In humans: 2n = 46 → n = 23 in each gamete; fertilisation restores diploid (23 + 23 = 46). Includes explicit pedagogical contrast with mitosis on the four mark-scheme dimensions: number of daughter cells (2 vs 4), chromosome count (maintained vs halved), genetic identity (identical vs different), and purpose (body cells vs gametes). Entire topic is HL only.