Now when our helicase binds to the origin of replication it begins to move more slowly. And as it moves, let's suppose it moves from right to left along the double stranded DNA molecule. It begins to unzip or unwind that double stranded DNA. And the way that it does it is by breaking these hydrogen bonds between our base pairs. And so now we have these single strands that are exposed. So as our bound helicase moves along the double stranded DNA molecule, it unwinds it even further.