meiosis

noun

(Gr. meioô: to reduce) The two-stage division of a diploid nucleus, occurring once in every sexual life cycle, in which gene recombination occurs and the number of chromosomes characteristic of the sporophyte plant is halved prior to the production of gametes. Two consecutive divisions occur. In the first, homologous chromosomes become paired and may exchange genetic material (see crossing over) before moving away from each other into separate daughter nuclei. This is the actual reduction division because each of the two nuclei so formed contains only half of the original chromosomes. The daughter nuclei then divide by mitosis and four haploid cells are produced. See also prophase; metaphase; anaphase; telophase. Syn. miosis.