Which enzyme is responsible for breaking the hydrogen bonds between base pairs during DNA replication?

Which enzyme is responsible for breaking the hydrogen bonds between base pairs during DNA replication?

• A. Topoisomerase
• B. Primase
• C. DNA helicase
• D. DNA ligase

Answer: (C)

Separating the two DNA strands requires breaking the hydrogen bonds that hold base pairs together. DNA helicase does this job by acting as the unwinding motor at the replication fork, using energy from ATP hydrolysis to pry the strands apart and create single-stranded templates for copying. The other enzymes have different roles: topoisomerase relieves the twisting tension that results from unwinding, primase lays down a short RNA primer to start synthesis, and DNA ligase seals the nicks after fragments are synthesized. So the enzyme that breaks the hydrogen bonds to unwind the DNA is helicase.

Separating the two DNA strands requires breaking the hydrogen bonds that hold base pairs together. DNA helicase does this job by acting as the unwinding motor at the replication fork, using energy from ATP hydrolysis to pry the strands apart and create single-stranded templates for copying. The other enzymes have different roles: topoisomerase relieves the twisting tension that results from unwinding, primase lays down a short RNA primer to start synthesis, and DNA ligase seals the nicks after fragments are synthesized. So the enzyme that breaks the hydrogen bonds to unwind the DNA is helicase.