[Meiosis].

Meiosis is the specialized pair of cell divisions that alter the genetic content of the nucleus from 2n (diploid) to 1n (haploid) and lead to the production of gametes. Following a premeiotic S phase, homologous chromosomes pair and synapses. This is followed by meiotic recombination and subsequent chiasmata formation between the paired homologous chromosomes. Chromosome pairing and the formation of chiasmata ensure the bipolar attachment of homologous chromosomes to the spindle, which is required for the reductional division of meiosis I that leads to the separation of homologs. This is followed by a modified cell cycle lacking an S phase. A second, equational division leads to the separation of sister chromatids and a halving of the chromosome number per cell. The general progression of meiosis is highly conserved, and is thus similar in yeast, humans, and plants.