What components comprise the replisome?

• A. Helicase, DNA polymerases, sliding clamp, primase, and ligase are coordinated at the replisome.
• B. Only helicase operates at the replisome.
• C. RNA polymerase and transcription factors form the replisome.
• D. Ligase alone constitutes the replisome.

Answer: (B)

The replisome is a coordinated, multi‑protein machine that unwinds DNA and builds two new strands at the same time. Helicase does the unwinding by moving along the DNA and separating the two strands at the replication fork. To start synthesis, primase lays down short RNA primers so DNA polymerases have a 3′ end to extend from. The leading strand is synthesized continuously by a DNA polymerase that remains attached to the template, aided by a sliding clamp that keeps the polymerase firmly engaged and a clamp loader that places the clamp in position. The lagging strand is synthesized in short segments called Okazaki fragments, each initiated by a primer and extended by polymerase until a turnover step occurs, after which ligase seals the resulting nicks to create a continuous strand. All of these activities are coordinated so both strands are replicated efficiently in parallel. So the replisome isn’t just one enzyme like helicase or ligase alone; it’s a collaborative assembly that includes helicase, primase, DNA polymerases, the sliding clamp, the clamp loader, and ligase working together.