Answer:
Nondisjunction is defined as the failure in the separation of homologous chromosomes or sister chromatids during nuclear division.
Nondisjunction occurs in both phases meiosis one (I) and meiosis two (II) during anaphase but both in both phases nondisjunction is different.
In meiosis I, homologous chromosomes fail to separate while in meiosis II, sister chromatids fail to separate.