Which enzyme unwinds the DNA during replication?

Which enzyme unwinds the DNA during replication?

• A. Helicase
• B. Ligase
• C. Primase
• D. Topoisomerase

Answer: (A)

During replication, the two DNA strands must be separated so that polymerases can copy each template. The enzyme that does this unwinding is helicase. It binds to the DNA and uses energy from ATP hydrolysis to break the hydrogen bonds between base pairs, opening the double helix and creating the replication fork. This unwinding is the essential first step, whereas ligase seals nicks in the backbone after synthesis, primase lays down RNA primers to start synthesis, and topoisomerase relieves twisting strain ahead of the fork without actively unwinding the strands itself.

During replication, the two DNA strands must be separated so that polymerases can copy each template. The enzyme that does this unwinding is helicase. It binds to the DNA and uses energy from ATP hydrolysis to break the hydrogen bonds between base pairs, opening the double helix and creating the replication fork. This unwinding is the essential first step, whereas ligase seals nicks in the backbone after synthesis, primase lays down RNA primers to start synthesis, and topoisomerase relieves twisting strain ahead of the fork without actively unwinding the strands itself.