During DNA replication, which enzyme unwinds the double helix?

During DNA replication, which enzyme unwinds the double helix?

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

Answer: (D)

When DNA is copied, the two strands must be separated so each can act as a template. The enzyme that does this unwinding is helicase. It binds to the DNA at the replication fork and uses energy from ATP to break the hydrogen bonds between bases, effectively unzipping the helix and exposing the single strands for copying. This unwinding is the crucial first step that allows DNA polymerase and the other enzymes to synthesize new DNA. Ligase’s job is to seal breaks in the sugar-phosphate backbone after synthesis. Primase lays down an RNA primer so DNA polymerase can start adding nucleotides. DNA polymerase actually builds the new DNA but cannot unwind the helix on its own. So helicase is the enzyme responsible for opening up the DNA, enabling replication to proceed.

When DNA is copied, the two strands must be separated so each can act as a template. The enzyme that does this unwinding is helicase. It binds to the DNA at the replication fork and uses energy from ATP to break the hydrogen bonds between bases, effectively unzipping the helix and exposing the single strands for copying. This unwinding is the crucial first step that allows DNA polymerase and the other enzymes to synthesize new DNA.

Ligase’s job is to seal breaks in the sugar-phosphate backbone after synthesis. Primase lays down an RNA primer so DNA polymerase can start adding nucleotides. DNA polymerase actually builds the new DNA but cannot unwind the helix on its own. So helicase is the enzyme responsible for opening up the DNA, enabling replication to proceed.