During gametogenesis, if nondisjunction occurs in meiosis II (meaning that that at least one pair of sister chromatids did not separate), the resultant effect will be two cells that has the normal haploid number of chromosomes (n), one cell that has an extra chromosome (n + 1), and one cell that has one missing chromosome (n - 1). In summary, two of the gametes will be n, one will be n + 1, one will be n — 1.
