So let's suppose we have a double stranded DNA molecule as shown on the board. Now, the second step of this process will involve DNA replication. And remember, DNA replication only takes place if the two strands of DNA have separated. So, in step one, what we essentially want to do is we want to denature the double helix structure of the DNA. We want to separate the two strands of DNA, and the way that we're going to separate them is by adding sodium hydroxide. So remember, a base or an acid, if we mix the DNA in either a basic or acidic solution, in this case a basic, the base will essentially ionize the bases of our DNA molecule and that will disrupt and break the hydrogen bonds.