Meiosis

Meiosis is a type of cell division that reduces chromosome number by half and reshuffles genetic material, producing haploid cells from a diploid cell.

Meiotic recombination: The exchange of DNA between homologous chromosomes during meiosis. Crossovers create new combinations of parental DNA before chromosomes separate.
Haploid: A cell or organism with one complete set of chromosomes. Meiosis produces haploid cells from a diploid starting cell.
Gametogenesis: The biological process that produces gametes, such as eggs and sperm. In animals, meiosis is a central stage in gamete production.
Mitosis: Cell division that typically produces two daughter cells with the same chromosome number as the parent. Unlike meiosis, mitosis does not halve chromosome number or pair homologs.
Aneuploidy: A chromosome-number abnormality in which a cell gains or loses individual chromosomes. Nondisjunction during meiosis can produce gametes with an abnormal chromosome count.
Synaptonemal complex: A protein structure that aligns homologous chromosomes during meiotic prophase I. It holds homologs together while they pair and exchange DNA.
Diploid: A cell or organism with two sets of chromosomes, typically one inherited from each parent. The usual meiotic starting cell contains homologous pairs.
Spermatogenesis: The process by which sperm cells develop from germ cells in the testes. Meiosis produces haploid cells that mature into sperm.
Binary fission: A form of cell division in which a prokaryotic cell copies its DNA and splits in two. It produces daughter cells without meiosis's paired homologs and two successive divisions.
Down syndrome: A genetic condition caused in most cases by an extra copy of chromosome 21. A meiotic chromosome-separation error can create the extra chromosome.

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