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The Biology of Crossing-over

Naturevolume 140pages759761 (1937) | Download Citation



SEXUAL reproduction consists of two alter-nating processes: fertilization, by which two germ cells containing each a single set of chromosomes fuse and produce a zygote with the double number of chromosomes, and meiosis, by which the double number is reduced and germ cells are again formed with the single number. As Weismann first pointed out, the biological importance of these processes is that they enable the hereditary differences between the chromosomes to be recombined in the greatest number of ways to give the greatest number of different individuals and therefore the greatest scope for natural selection to act in directing evolutionary change.


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