What metaphase does nondisjunction occur in Metaphase 1 or metaphase 2?

Answer 1

Non-disjunction is the failure of a pair of chromosomes or chromatids to separate. Since this happens in both metaphase I and II, non-disjunction can occur in either stage.

In metaphase I it is the failure of the two homologous chromosomes in the pair to separate. In this case all of the gametes will be affected.

In metaphase II it is the failure of the two sister chromatids to separate. In this case only half of the gametes are affected.

Non-disjunction is the cause of a number of genetic conditions eg Down syndrome, Triple-X syndrome.

See http://en.wikipedia.org/wiki/Nondisjunction

Answer 2

Nondisjunction can occur in both Metaphase 1 and Metaphase 2 of meiosis. In Metaphase 1, it results in the incorrect separation of homologous chromosomes, leading to aneuploidy in the daughter cells. In Metaphase 2, it can lead to the incorrect separation of sister chromatids, also resulting in aneuploidy.

Answer 3

Yes crossing over can occur in metaphase 1 and metaphase 2