NEETBotanyCell Cycle and Cell Division
During the pachytene stage of prophase I, recombination nodules appear on the bivalents to mark the sites of crossing over. Which of the following correctly describes the nature of this crossing over process?
Options
- AIt is a non-enzymatic physical breakage and reunion of chromatids.
- BIt is an enzyme-mediated process primarily involving the enzyme recombinase.
- CIt is an enzyme-mediated process primarily involving DNA ligase only.
- DIt is an enzyme-mediated process primarily involving RNA polymerase.
Correct answer
B. It is an enzyme-mediated process primarily involving the enzyme recombinase.
Step-by-step solution
According to NCERT, crossing over occurs during the pachytene stage of prophase I in meiosis. It is characterised by the appearance of recombination nodules, which mark the sites where the exchange of genetic material takes place between non-sister chromatids of homologous chromosomes. Crossing over is strictly an enzyme-mediated process. The specific enzyme complex involved in this recombination process is called recombinase. It does not occur through mere physical breakage without enzymes, nor are DNA ligase or R