Which enzyme unwinds the DNA double helix during replication?

Which enzyme unwinds the DNA double helix during replication?

• A. DNA polymerase
• B. Helicase
• C. Ligase
• D. Primase

Answer: (B)

DNA must be opened up to expose the template strands for replication, and this unwinding is accomplished by helicase. Helicase uses energy from ATP to break the hydrogen bonds between base pairs as it moves along the DNA, separating the two strands and forming the replication fork. Once the strands are separated, primase lays down RNA primers and DNA polymerase begins synthesizing new DNA from those primers. Ligase then seals the gaps between fragments on the new strand. Topoisomerase helps relieve the twisting tension ahead of the fork, but the actual unwinding action is carried out by helicase.

DNA must be opened up to expose the template strands for replication, and this unwinding is accomplished by helicase. Helicase uses energy from ATP to break the hydrogen bonds between base pairs as it moves along the DNA, separating the two strands and forming the replication fork. Once the strands are separated, primase lays down RNA primers and DNA polymerase begins synthesizing new DNA from those primers. Ligase then seals the gaps between fragments on the new strand. Topoisomerase helps relieve the twisting tension ahead of the fork, but the actual unwinding action is carried out by helicase.