Discuss the molecular mechanism of crossing over.
Mechanism of crossing over:
The figure shows that crossing over, leading to recombination of linked genes, is due to interchange of sections of homologous chromosomes. At meiosis, the homologous (maternal and paternal) chromosomes come together and pair, or synapse, during prophase. The pairing is remarkably precise and is evidently brought about by mutual attraction of the parts of the chromosomes that are similar or homologous because they contain allellic genes.
Further, during the transition between the pachytene and the diplotene of the prophase of meiosis, the paired chromosomes divide each into two chromatids, so that the bivalent is now composed of four chromatids. At about the time when the chromosomes are first seen to be divided, the chromatids establish one or more exchange, or Chiasmata, per bivalent.
At each chiasma, two of the chromatids have become broken and then rejoined, so that the new
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