Nondisjunction (redirected from Chromosome nondisjunctions)

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. 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).

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non·dis·junc·tion (nnds-jngkshn)

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.

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nondis·junction·al adj.

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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

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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.