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If there was crossing over in mitosis, then there would various nature of somatic cells. May be that's the logic, but what is the mechanism? Why are there no crossover events during mitosis?

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    $\begingroup$ en.wikipedia.org/wiki/Mitotic_crossover $\endgroup$ – fileunderwater Feb 19 '15 at 20:36
  • $\begingroup$ During mitosis both sister chromatids are identical si there would be no benefit to crossing over. During mieosis a person receives one chromosome from each parent which will encourage homologous recombination or crossing over to promote gebetic diversity. $\endgroup$ – I-heart-XBP1 Feb 24 '15 at 16:42
  • $\begingroup$ during mitosis both sister chromatids are identical so no benifit of crossing over..During meiosis there are paternal and maternal chromosomes so crossing over promote genetid variability. $\endgroup$ – nadia Apr 4 '17 at 7:51
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It can actually on very rare occasions however, it is also highly problematic and generally creates deleterious mutations and can inactivate genes. Depending on the location of the cell and the cross-over within the genome, it can also contribute to the formation of cancer. For instance, in the case of retinoblastoma, if there is one mutated copy of RAS on one chromosome and a normal copy on the other and mitotic crossing over occurs, then you can potentially remove the protective nonmutant copy of RAS from one of the daughter cells. This cell is then one step closer to becoming tumorgenic.

Thus, one reason this may not occur ordinarily is to reduce the chance of causing such a cancer. As for why it does occur on the rare times it does, I am not certain as of the time of writing this.

Reference: The Biology of Cancer, by Robert A. Weinberg

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The mechanism is straightforward: in Metaphase I of Meiosis, chromosomes line up in two lines, with homologous across from each other, which allows them to interact by crossing over. In Metaphase of Mitosis, the chromosomes are all lined up single file, so the homologous chromosomes cannot interact.

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  • $\begingroup$ This seems to contradict the possibility of mitotic crossover. $\endgroup$ – March Ho Feb 20 '15 at 11:30
  • $\begingroup$ Yes, but mitotic crossover does not usually happen. It's more of a bug than a feature. $\endgroup$ – Breaking Bioinformatics Feb 22 '15 at 18:08

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