What is the function of topoisomerase during DNA replication?

What is the function of topoisomerase during DNA replication?

• A. Synthesize RNA primers
• B. Relieve torsional strain ahead of the replication fork
• C. Unwind the DNA double helix
• D. Join Okazaki fragments

Answer: (B)

During DNA replication, the two strands are pulled apart by helicase, which creates twisting and tension ahead of the replication fork. If that torsional strain isn’t relieved, the fork would stall. Topoisomerase solves this by making transient breaks in the DNA backbone, allowing the helix to swivel and release the supercoiling. After the tension is relieved, the breaks are resealed, so replication can proceed smoothly. This role is distinct from primase, which makes RNA primers; from helicase, which unwinds the strands; and from ligase, which seals gaps between Okazaki fragments.

During DNA replication, the two strands are pulled apart by helicase, which creates twisting and tension ahead of the replication fork. If that torsional strain isn’t relieved, the fork would stall. Topoisomerase solves this by making transient breaks in the DNA backbone, allowing the helix to swivel and release the supercoiling. After the tension is relieved, the breaks are resealed, so replication can proceed smoothly. This role is distinct from primase, which makes RNA primers; from helicase, which unwinds the strands; and from ligase, which seals gaps between Okazaki fragments.