During DNA replication, which enzyme unwinds ("unzips") the double helix by breaking hydrogen bonds between base pairs at the replication fork?

• A. DNA helicase
• B. DNA polymerase III
• C. Primase
• D. DNA ligase

Answer: (A)

Verified step by step guidance

1. Understand the process of DNA replication, which involves unwinding the double helix to allow the synthesis of new DNA strands.
2. Identify the role of enzymes involved in DNA replication: DNA polymerase III synthesizes new DNA strands, primase synthesizes RNA primers, DNA ligase joins Okazaki fragments, and DNA helicase unwinds the DNA.
3. Focus on the enzyme responsible for breaking the hydrogen bonds between complementary base pairs to separate the two strands at the replication fork.
4. Recall that the enzyme which 'unzips' the DNA by breaking hydrogen bonds is DNA helicase.
5. Conclude that DNA helicase is the enzyme that unwinds the double helix during DNA replication.