Failure of a pair of homologous chromosomes to separate during after cell division. It occurs during the anaphase of meiosis. It can also occur during and after mitosis when sister chromatids fail to separate. Non-dysjunction can result when daughter cells have a relative abnormal number of chromosomes. The outcomes include, for example, Down’s syndrome and Turner’s syndrome.
See Anaphase, Chromatid, Chromosome, Down’s syndrome, Meiosis (or reduction division), Mitosis, Turner’s syndrome