The enzyme helicase is responsible for separating the DNA strands during replication.

Here's how it works:

1. Binding: Helicase binds to the DNA double helix at the origin of replication.

2. Unwinding: Helicase uses energy from ATP to break the hydrogen bonds between the nitrogenous bases of the two strands.

3. Separation: This unwinding action creates a replication fork, a Y-shaped structure where the two strands are separated.

This separation allows other enzymes, like DNA polymerase, to access the single strands and begin synthesizing new complementary strands.