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 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: -Errors can occur during meiosis producing gametes with an extra or missing chromosome. The consequences of this following fertilisation depend on which chromosomes are affected. Often the embryo is not viable, but some of these errors can lead to trisomy conditions or sex chromosome disorders.

Detailed explanation-4: -During anaphase 1 chromosome separate and go to opposite poles while during anaphase 2 sister chromosomes separate. It is called is disjunction. Sometimes the separation is not normal and it is called non-disjunction.

Detailed explanation-5: -Disjunction is the normal separation or moving apart of chromosomes toward opposite poles of the cell during cell division. Disjunction normally occurs during the anaphase of mitosis and meiosis (I and II).