AP BIOLOGY

Detailed explanation-1: -In nondisjunction, the separation fails to occur causing both sister chromatids or homologous chromosomes to be pulled to one pole of the cell. Mitotic nondisjunction can occur due to the inactivation of either topoisomerase II, condensin, or separase.

Detailed explanation-2: -Nondisjunction is the failure of homologous chromosomes (chromatids) to separate properly during meiotic cell division.

Detailed explanation-3: -There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis. Nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy).

Detailed explanation-4: -Nondisjunction, in which chromosomes fail to separate equally, can occur in meiosis I (first row), meiosis II (second row), and mitosis (third row). These unequal separations can produce daughter cells with unexpected chromosome numbers, called aneuploids.

Detailed explanation-5: -In the first type, due to nondisjunction during meiosis I, homologous chromosomes fail to segregate at anaphase I and lead to all the haploid cells with an abnormal number of chromosomes. The second type of nondisjunction occurs during meiosis II when sister chromatids fail to segregate.