Which enzyme unwinds the DNA double helix during replication and what energy source does it use?

Which enzyme unwinds the DNA double helix during replication and what energy source does it use?

• A. DNA polymerase uses ATP to unwind.
• B. Ligase uses GTP to unwind.
• C. Helicase uses ATP to unwind.
• D. Primase uses ATP to unwind.

Answer: (C)

Unwinding the DNA double helix at the replication fork is done by helicase, an enzyme that breaks the hydrogen bonds between base pairs as it moves along the DNA. It uses energy from ATP hydrolysis to power its translocation and separation of the strands, creating the single-stranded templates needed for replication. The other enzymes listed don’t perform unwinding: polymerase isn’t the unwinding motor and uses nucleotides for synthesis; primase makes RNA primers using NTPs; ligase seals nicks but doesn’t unwind the strands. So helicase coupled with ATP hydrolysis is the correct pairing.

Unwinding the DNA double helix at the replication fork is done by helicase, an enzyme that breaks the hydrogen bonds between base pairs as it moves along the DNA. It uses energy from ATP hydrolysis to power its translocation and separation of the strands, creating the single-stranded templates needed for replication. The other enzymes listed don’t perform unwinding: polymerase isn’t the unwinding motor and uses nucleotides for synthesis; primase makes RNA primers using NTPs; ligase seals nicks but doesn’t unwind the strands. So helicase coupled with ATP hydrolysis is the correct pairing.