During replication, which enzyme unwinds the DNA double helix?

The enzyme that unwinds the DNA double helix during replication is helicase. This enzyme plays a crucial role at the start of DNA replication by breaking the hydrogen bonds between the complementary strands of DNA, allowing the double helix to separate into two single strands. By doing so, helicase facilitates access for other enzymes that will perform additional functions in the replication process.

In contrast, ligase is involved in joining DNA fragments together, particularly in the lagging strand where Okazaki fragments need to be connected. Primase synthesizes a short RNA primer that provides a starting point for DNA synthesis, which is essential for the action of DNA polymerase. DNA polymerase is responsible for adding nucleotides to the growing DNA strand during replication. Each of these enzymes has a distinct role, but helicase is specifically tasked with unwinding the DNA, making it essential for successful replication.