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.A cell biologist examines the final products of meiosis in an earthworm (2n=36)and finds 2 cells with 20 chromosomes,and 2 cells with 16 chromosomes.Most likely this was because

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The fact that there are both cells with 20 and 16 chromosomes suggests that there was a non-disjunction event during meiosis I, as 2 pairs of homologous chromosomes failed to separate. If a pair of sister chromatids had failed to separate during meiosis II, we would expect all 4 resulting cells to have the same number of chromosomes (either 18 or 19), as there would have been a non-disjunction event in both cells.

Non-Disjunction Is the Failure of Homologous Chromosomes to Separate During