![]() These random cross-over events scrambles the genetic material of each of the chromosomes in the gametes, helping to produce diverse offspring. This exhange of genetic material between maternal and paternal chromosomes is known as 'genetic recombination'Įach cross-over between two non-sister chromatids is called a chiasma (plural 'chiasmata') Each cross-over between two non-sister chromatids is called a chiasma (plural 'chiasmata') On average, 2-3 cross-overs per chromosome occur for humans. In the long prophase of meiotic division 1, genetic material can 'cross over' between maternal and paternal pairs of chromosomes (non-sister chromatids). Homologous chromosomes duplicate, but remain separate. However, in meiosis, the two pairs of chromosomes (paternal and maternal) stay together on the spindle of the equator to form a bivalent (contains 4 chromatids) The arms of sister chromatids are glued together by a protein called 'cohesin'. Homologous chromosomes duplicate to form sister chromatids, as in mitosis. The chromosomes in this pair are called homologs - there is one paternal and one maternal homolog.One of these chromosomes is derived from the male parent (parental chromosome) and one from the female (maternal chromosome).A diploid nucleus contains two pairs of each type of chromosome (autosomes) together with the sex chromosomes (X and X, or X and Y).Meiosis is from the greek work for 'diminuition'. That on the right shows mitotic (normal) cell division. The diagram on the left shows meiotic cell division.
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