And that implies that DNA replication only takes place at one location and at one position on that prokaryotic DNA molecule. Now what exactly takes place once the DNA helicase enzyme actually binds to the origin of replication? Well, let's take a look at the following diagram that describes what is taking place. So this is our helicase molecules. So let's suppose the helicase enzyme moves along our DNA molecule very quickly until it reaches the origin of replication which is shown here. Now notice that each one of these pair of bases are held together by hydrogen bonds.