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The random organisation of chromosomes in the middle of the cell during the first stage of meiosis, which further increases genetic diversity.

Use in clinical context

Meiosis produces an individual’s gametes. During the first stage of meiosis (meiosis I), the homologous chromosomes line up in the middle of the cell before being separated into two new cells. One of each pair of homologous chromosomes originated in the individual’s mother and the other in their father. Which side of the spindle each chromosome lines up on is random and, due to the number of chromosomes in the genome, the potential combinations are in the millions. This results in some chromosomes that were from the individual’s mother on one side and others inherited from their father on the opposite side. Consequently, when these are pulled apart there will be a mixture of maternal and paternal chromosomes in the newly formed cells. Random assortment contributes to the mixing up of genetic material in the gametes. This means that, although siblings often resemble each other, they are never identical unless they are monozygotic twins.

Last updated on 30th May, 2019