Cell Cycle and Cell Division Question 40
40. Crossing over takes place between which chromatids and in which stage of the cell cycle?
[2019, Odisa]
(a) Non-sister chromatids of non-homologous chrom-osomes at Pachytene stage of prophase I.
(b) Non-sister chromatids of non-homologous chrom-osomes at Zygotene stage of prophase I.
(c) Non-sister chromatids of homologous chromosomes at Pachytene stage of prophase I.
(d) Non-sister chromatids of homologous chromosomes at Zygotene stage of prophase I.
Show Answer
Answer : c
Hints & Solutions
(c) Crossing over is the exchange of gene which takes place between non-sister chromatids of homologous chromosomes at pachytene stage of meiosis I resulting in new allelic combinations in the daughter cells. Crossing over is essential for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical.
