Question

Nondisjunction 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 ____

Answer 1

Most likely this was failure of nondisjunction occurred during meiosis I resulted with 2 pairs of homologous chromosomes failed to separate. Step-by-step explanation:

Simple explanation is that if nondisjunction occurs in meiosis II, there would be 3 types of cells; n-2, n-1 and n. And if nondisjunction occurs in meiosis I there would be two types of cells n+2 and n-2 (see figure). If the 2n = 36 than n should equal to the 18. There are two types of cells n +2 (20 chromosomes) and n-2 (16 chromosomes) so answer is "nondisjunction in meiosis I".