We want to break apart these two molecules because ultimately we only want the red molecule and not the blue molecule. Now, recall in our discussion of nucleic acids we said that DNA molecules are more stable than RNA molecules. In fact, if we increase the PH, if we make our solution very basic DNA molecules will remain intact but RNA molecules will be destroyed, will be hydrolyzed. And so if we take the DNA RNA complex and we increase the PH so we create a basic solution. The RNA will be hydrolyzed while the DNA will remain intact. And so after step three, we essentially isolate that individual strand of complementary DNA shown in red.