Definition of nondisjunction in US English:



  • The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

    • ‘Although this assay is very sensitive for detecting chromosomal loss, it is unable to detect non-disjunction and chromosome gain.’
    • ‘Although the non-disjunction of chromosome 21 in cultured lymphocytes was reported to be increased by age, there was no age or sex effect on chromosome 21 micronucleation in healthy persons.’
    • ‘For example, a family history of multiple relatives with Down syndrome suggests an inherited translocation, not sporadic non-disjunction.’
    • ‘In principle, non-disjunction during spermatogenesis could lead to aneuploidy, which might cause fetal death.’
    • ‘The origin of the extra chromosome 21 due to meiotic non-disjunction was 79.24 per cent maternal and 20.76 per cent paternal.’