What enzymes are key in the DNA replication process?

What enzymes are key in the DNA replication process?

• A. DNA ligase and primase
• B. Topoisomerase and Helicase
• C. RNA polymerase and ligase
• D. Nuclease and polymerase

Answer: (B)

The key idea is that DNA replication needs enzymes that open up the DNA and keep it from getting tangled so the copies can be made. Helicase is the unwinding engine—it uses energy to separate the two DNA strands at the replication fork, giving the replication machinery access to the bases. Topoisomerase is the untangler—it relieves the positive supercoiling and torsional strain that builds up ahead of the fork as unwinding progresses, preventing knots and breaks in the DNA. Together, these two enzymes set the stage for copying the genome. Other enzymes like primase, DNA polymerase, and ligase are also crucial for synthesis and joining fragments, but the pair that directly enables the fork to advance by unwinding and relieving torsion is topoisomerase and helicase.

The key idea is that DNA replication needs enzymes that open up the DNA and keep it from getting tangled so the copies can be made. Helicase is the unwinding engine—it uses energy to separate the two DNA strands at the replication fork, giving the replication machinery access to the bases. Topoisomerase is the untangler—it relieves the positive supercoiling and torsional strain that builds up ahead of the fork as unwinding progresses, preventing knots and breaks in the DNA.

Together, these two enzymes set the stage for copying the genome. Other enzymes like primase, DNA polymerase, and ligase are also crucial for synthesis and joining fragments, but the pair that directly enables the fork to advance by unwinding and relieving torsion is topoisomerase and helicase.