The enzyme that unwinds the double helix of DNA in preparation for DNA replication is called:

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

Answer: (B)

Verified step by step guidance

1. Understand the context: DNA replication is the process by which a cell duplicates its DNA before cell division. This involves several enzymes, each with a specific role.
2. Identify the role of the enzyme in question: The enzyme that unwinds the double helix of DNA is responsible for separating the two strands of DNA to create a replication fork, allowing other enzymes to access the DNA template.
3. Review the function of each enzyme listed: Primase synthesizes RNA primers, DNA polymerase adds nucleotides to the growing DNA strand, ligase seals gaps in the DNA backbone, and helicase unwinds the DNA double helix.
4. Focus on helicase: Helicase is the enzyme that breaks the hydrogen bonds between complementary base pairs, effectively unwinding the DNA double helix at the replication fork.
5. Conclude that the correct answer is helicase, as it specifically performs the unwinding function necessary for DNA replication to proceed.