Question

Write a note on crossing over.

Answer 1

Crossing-over is the process by which homologous chromosomes exchange segments with each other. It occurs most often during the first meiotic division. When prometaphase begins, each chromosome has been duplicated to form two identical sister chromatids. Crossing-over takes place between homologous pairs of chromosomes, with sister chromatids of each homolog swapping segments at various places along the length of the chromosome. Crossing over also occurs between sister chromatids, but because they are genetically identical, such crossing over will not result in genetic recombination.





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Answer 2

DNA strands must be broken to exchange their segments. The portions of the chromosome that undergo crossing over contain the same gene loci. Crossing-over leads to the recombination of the genes on the chromosomes. The point of crossover is visible as a cross-shaped chiasma.