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During recombination, is the number of chiasmata consistent for each gamete and are the chiasmata regions consistent within a single organism?

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  • $\begingroup$ Welcome to Biology.SE. What do you mean by [..] are the chiasmata regions consistent within a single organism?? Do you mean "Are there regions of high recombination rate and other regions of low recombination rate?"? $\endgroup$
    – Remi.b
    Jan 17, 2016 at 19:30
  • $\begingroup$ Maybe I should rephrase the question, how many recombination events occur in a single germ cell? Is recombination really random or is recombination deterministic? If not, what influences randomness in recombination. Does the cell nucleus secrete some enzyme the randomly glues homologous chromosomes at random sites? $\endgroup$
    – AminomiX
    Jan 18, 2016 at 20:04

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There is a large amount of variation in the distribution and number of chiasmata or crossing overs (COs). The total number of chiasmata per cell can vary within the same organism. Where chiasmata occur along the chromosome is also not consistent cell to cell. Hotspots are 1-2kb regions that experience elevated recombination compared to neighboring genomic regions. A way to think of the distribution of COs is that ~80% of recombination happens in hotspots which comprise ~10% of the genome.

Recombination depends on the chromatin context, so chiasmata are rare near the centromere and positive interference results in chiasmata being spaced out along the chromosome. A good prediction of total chiasmata number per cell is at least 1 per chromosome. Some researchers argue that one CO per chromosome arm is more accurate.

Below is a link to a good article that expands on some of the ways recombination varies in humans. http://www.nature.com/nrg/journal/v8/n1/abs/nrg1947.html

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  • $\begingroup$ Thanks!!! Your answer along with the article turned out to be very helpful!!! $\endgroup$
    – AminomiX
    Jan 18, 2016 at 20:07

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