Non-disjunction is the failure of homologous chromosomes to separate during meiosis i, or the failure of sister chromatids to separate during meiosis ii or mitosis. as a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. this produces daughter cells with an imbalance of chromosomes. if 22 pairs of homologous chromosomes segregate normally during meiosis i in humans (n=23) but we have non-disjunction of 1 pair, then at the end of meiosis ii we will have: