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The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.

non′dis·junc′tion·al adj.


(Genetics) the failure of paired homologous chromosomes to move to opposite poles of the cell during meiosis
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Noun1.nondisjunction - meiosis in which there is a failure of paired homologous chromosomes to separate; results in an abnormal number of chromosomes in the daughter cells
meiosis, miosis, reduction division - (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants)
References in periodicals archive ?
3] Three different mechanisms can lead to triploidy: (i) a non-disjunction event in meiosis 1 or 2 of spermatogenesis; (ii) non-disjunction in meiosis 1 or 2 of oogenesis; and (iii) dispermy.
Finally, through non-disjunction some of the paired chromosomes representing paired linkage groups may not separate during synapsis and therefore more than the ordinary simplex number may be present in a portion of the mature germ cells.
The main cause of deterioration of oocyte quality is meiotic non-disjunction (20).
Investigations on Drosophila melanogaster indicated developed abnormalities due to the effect of mutagenic factors on meiotic chromosomal non-disjunction (Ramel, 2003).
The embryological etiology of DS is mainly correlated with the non-disjunction of a chromosome 21 during la maternal meiosis (4); this consists of errors occurring during the separation of homologous chromatid pairs.

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