But in DNA the complementary sequences in the double helix structure come from two opposite polynucleotide chains. So that's the difference between the double helix in DNA and the double helix in RNA molecules. So we have these complementary sections that interact to form hydrogen bonds and that's a stabilizing effect. While this is the loop, they contain the mismatched nucleotides and that means they cannot interact and so they will destabilize this localized region of space in our RNA molecule. Now, just like in proteins we have this tertiary structure and secondary structure. RNA molecules can also form secondary and tertiary structures.