Q.What is crossing over?
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Start your 14-day free trial to unlock the full solution →Crossing over is the exchange of DNA segments between non-sister chromatids of paired homologous chromosomes during meiosis, producing new combinations of alleles.
During meiosis, homologous chromosomes pair closely together (synapsis) at zygotene to form bivalents. At the next sub-stage, PACHYTENE, the four chromatids of each bivalent become visible, and the non-sister chromatids (one from each homolog) develop contact points called chiasmata, at which they break and rejoin, physically exchanging corresponding segments of DNA. This exchange is CROSSING OVER. Because the exchanged segments carry genes/alleles, crossing over recombines the maternal and paternal alleles onto the same chromosome, producing chromatids with new combinations of traits not p …
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