Which enzyme unwinds the double helix and breaks hydrogen bonds to allow replication?

• A. DNA Ligase
• B. DNA Polymerase
• C. DNA Helicase
• D. RNA Polymerase

Answer: (C)

DNA Helicase is the enzyme that unwinds the double helix by breaking the hydrogen bonds between base pairs, using energy from ATP to move along the DNA and create a replication fork. This opening step is essential so DNA polymerases can access each parental strand and synthesize the new strands. The other enzymes have different roles: ligase seals nicks in the backbone after fragments are formed; DNA polymerase builds the new DNA but cannot separate the strands by itself; RNA polymerase (primase) makes RNA primers but is not the enzyme that unwinds the helix.