Question

What is the role of Topoisomerase during the process of DNA replication?

• A. Synthesizes RNA primers
• B. Unwinds the DNA helix
• C. Relieves supercoiling ahead of the replication fork
• D. Joins Okazaki fragments

Hint:

{Replication enzymes memory trick:}
Helicase → Unwinds DNA
Topoisomerase → Relieves supercoiling
Ligase → Joins Okazaki fragments

Answer 1

The Correct Option is C

Concept: During DNA replication, the double helix must unwind to allow replication machinery to access the DNA strands. This unwinding creates tension and supercoiling ahead of the replication fork, which must be relieved to allow replication to continue smoothly.
Step 1:Action of helicase.
DNA helicase unwinds the double helix by breaking hydrogen bonds between complementary base pairs. This unwinding generates torsional strain and supercoiling in the DNA ahead of the replication fork.
Step 2:Role of topoisomerase.
Topoisomerase enzymes relieve this tension by temporarily cutting one or both strands of the DNA molecule.
Step 3:Relief of supercoiling.
After cutting the DNA, topoisomerase allows the DNA strands to rotate and release the accumulated tension. The enzyme then reseals the broken DNA strands. This process prevents excessive twisting and ensures smooth progression of the replication machinery. Thus, the primary role of topoisomerase during DNA replication is to relieve supercoiling ahead of the replication fork.