NEET BIOLOGY

Detailed explanation-1: -Nondisjunction can occur during anaphase of mitosis, meiosis I, or meiosis II. During anaphase, sister chromatids (or homologous chromosomes for meiosis I), will separate and move to opposite poles of the cell, pulled by microtubules.

Detailed explanation-2: -Nondisjunction occurs when homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis. An individual with the appropriate number of chromosomes for their species is called euploid; in humans, euploidy corresponds to 22 pairs of autosomes and one pair of sex chromosomes.

Detailed explanation-3: -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-4: -In meiosis, disjunction happens when homologous chromosomes move apart toward the opposite poles of the cell in anaphase I. Disjunction again occurs when sister chromatids separate and move away from each other during anaphase II. Related term: disjunction mutant.

Detailed explanation-5: -If nondisjunction occurs during Meiosis I in humans, two gametes with extra chromosomes will be produced (24 chromosomes each, or n+1) and two gametes lacking a chromosome will be produced (22 chromosomes each, n-1).