Which enzyme is responsible for unwinding the DNA helix during replication?

The enzyme responsible for unwinding the DNA helix during replication is helicase. This enzyme plays a crucial role in the DNA replication process by separating the two strands of the DNA double helix, allowing each strand to serve as a template for the synthesis of a new complementary strand.

Helicase works by breaking the hydrogen bonds between the base pairs of the DNA strands, thus facilitating the access of other enzymes, like DNA polymerase, to replicate the genetic material. This unwinding action is vital for the replication fork to form, which is where the actual replication occurs.

Other enzymes mentioned, such as DNA polymerase, topoisomerase, and ligase, have important but distinct functions during replication. DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template strand, topoisomerase helps relieve the tension created ahead of the replication fork by making cuts in the DNA, and ligase is responsible for joining Okazaki fragments on the lagging strand.