non-disjunction
/ˌnɒndɪsˈdʒʌŋkʃən/noun
mass noun
- Genetics 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【遗传】（染色体的）不分离, 不分开。