During DNA replication, which enzyme is responsible for unzipping (unwinding) the DNA double helix at the replication fork?

• A. DNA ligase
• B. Primase
• C. DNA polymerase III
• D. DNA helicase

Answer: (D)

Verified step by step guidance

1. Understand the process of DNA replication, which involves unwinding the double helix, synthesizing new strands, and joining fragments.
2. Identify the role of each enzyme listed: DNA ligase joins Okazaki fragments, primase synthesizes RNA primers, and DNA polymerase III extends the new DNA strand.
3. Recall that the enzyme responsible for unzipping or unwinding the DNA double helix at the replication fork is the one that breaks hydrogen bonds between base pairs.
4. Recognize that DNA helicase is the enzyme that performs this unzipping function by separating the two strands to allow replication machinery access.
5. Conclude that DNA helicase is the correct enzyme responsible for unwinding the DNA during replication.