PATHOLOGY

Detailed explanation-1: -Meiotic Nondisjunction. Meiotic nondisjunction errors are common in humans, resulting in aneuploidy, a term used when the total number of chromosomes in a cell is not an exact multiple of the haploid number. Aneuploidy usually involves a single chromosome, but in rare circumstances, may involve more than one.

Detailed explanation-2: -Nondisjunction is caused due to inactivation of topoisomerase II, separase or condensin. During anaphase, the cohesin which binds the sister chromatids together is broken by separase. Catenation is removed by condensin and topoisomerase II. Segregation of chromosomes is regulated by spindle assembly checkpoint or SAC.

Detailed explanation-3: -Disjunction takes place again in Anaphase II of meiosis, when the sister chromatids separate and move to the opposite poles. To compare this with non-disjunction is when this process of separation of chromatids (mitosis) and homologous chromosomes (meiosis) fails to occur.