When does nondisjunction occur?

Answer 1

Nondisjunction occurs during cell division when chromosomes fail to separate properly. This can happen during meiosis or mitosis:

1. Meiosis: Nondisjunction can occur during either of the two meiotic divisions (meiosis I or meiosis II). In meiosis I, homologous chromosomes fail to separate, leading to gametes with an abnormal number of chromosomes. In meiosis II, sister chromatids fail to separate, which can also result in gametes with an abnormal chromosome number.

2. Mitosis: In mitosis, nondisjunction can occur when sister chromatids do not separate properly during the anaphase stage, resulting in daughter cells that have an abnormal number of chromosomes.

The result of nondisjunction is often aneuploidy, which is a condition where cells have an abnormal number of chromosomes, leading to various genetic disorders. Examples of conditions caused by nondisjunction include Down syndrome (trisomy 21), Turner syndrome (monosomy X), and Klinefelter syndrome (XXY).