nondisjunction /-disjungk″chən/ [L, non + disjungere, to disjoint] , failure of homologous pairs of chromosomes to separate during the first meiotic division or of the two chromatids of a chromosome to split during anaphase of mitosis or the second meiotic division. The result is an abnormal number of chromosomes in the daughter cells. Compare disjunction. See also monosomy, trisomy.
