Which function is not typically performed by the leading-strand replication proteins?

Which function is not typically performed by the leading-strand replication proteins?

• A. Unwinding the helix
• B. Stabilizing single strands
• C. Relieving torsional strain
• D. Sealing nicks in the backbone

Answer: (D)

Leading-strand replication proteins focus on keeping the DNA open for synthesis and managing the physical stress of unwinding. Helicase unwinds the double helix ahead of the fork, single-strand binding proteins stabilize the exposed DNA to prevent reannealing and protect it, and topoisomerase relieves the torsional strain that builds up as the helix unwinds. Sealing nicks in the backbone, however, is done by DNA ligase, which mainly acts on the lagging strand to join Okazaki fragments and during repair. So sealing nicks is not a typical activity of the leading-strand replication machinery.

Leading-strand replication proteins focus on keeping the DNA open for synthesis and managing the physical stress of unwinding. Helicase unwinds the double helix ahead of the fork, single-strand binding proteins stabilize the exposed DNA to prevent reannealing and protect it, and topoisomerase relieves the torsional strain that builds up as the helix unwinds. Sealing nicks in the backbone, however, is done by DNA ligase, which mainly acts on the lagging strand to join Okazaki fragments and during repair. So sealing nicks is not a typical activity of the leading-strand replication machinery.