nondisjunction /non·dis·junc·tion/ (-dis-junk´shun) failure either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. 
Nondisjunction
nondisjunction
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Nondisjunction. Normal meiosis (A) is contrasted with failure of homologous chromosomes to separate in meiosis I (B) or of sister chromatids to separate in meiosis II (C).
non·dis·junc·tion (n n d s-j ngk sh n)n. The failure of one or more pairs of chromosomes to separate at the miotic stage of karyokinesis, with the result that both chromosomes are carried to one daughter cell and none to the other. non dis·junction·al adj. |
Nondisjunction
A genetic term referring to an event which takes place during cell division, in which a genetic accident causes an egg or sperm cell to have 24 chromosomes, rather than the normal 23.
Mentioned in: Down Syndrome
nondisjunction
[-disjungk′chən]
Etymology: 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.
nondisjunction
failure (1) of two homologous chromosomes to pass to separate cells during the first division of meiosis, or (2) of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. Death of the fetus or chromosomal anomalies may result.
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