The enzyme that unwinds DNA to initiate replication is called helicase.

Here's how it works:

* Breaking Hydrogen Bonds: Helicase breaks the hydrogen bonds between the nitrogenous bases of the two DNA strands, separating them into two single strands.

* Unwinding the Double Helix: This process unwinds the double helix, creating a replication fork where the strands can be copied.

* Essential for Replication: Helicase's action is crucial for DNA replication, allowing the DNA polymerase enzymes to access the single strands and build new complementary strands.

Let me know if you'd like to know more about the process of DNA replication!