Cell biology. A specialised form of nuclear division in which there are two successive nuclear divisions (meiosis I and II) without any chromosome replication between them. Meiosis reduces the starting number of 4n chromosomes in the parent cell to n in each of the 4 daughter cells. Each cell receives only one of each homologous chromosome pair, with the maternal and paternal chromosomes being distributed randomly between the cells.
During the prophase of meiosis I homologous chromosomes pair to form bivalents, thus allowing crossing over, the physical exchange of chromatid segments. This results in the recombination of genes. Meiosis occurs during the formation of gametes (oogenese and spermatogenesis).