Nondisjunction is the unequal distribution of chromosomes during meiosis. Nondisjunction can occur at two different points. Either the homologues fail to separate during meiosis I or:
a) the sister chromatids fail to separate during meiosis I.
b) sister chromatids fail to separate during meiosis II.
c) the homologues all go into the same gamete during meiosis II.
d) the sister chromatids separate too soon in meiosis I.
e) the homologues fail to separate during meiosis II.
Answer: sister chromatids fail to separate during meiosis II.