Now, what about RNA molecules? Well, RNA molecules because they contain a slightly different sugar molecule they don't form the double helix. They exist predominantly as a single strand but they can also intertwine fold to form different types of tertiary and secondary structures. So what about the function of DNA and RNA? So the entire purpose of these nucleic acids is to basically store the genetic code, the genetic information in the cell and use it to build different types of proteins. And when the time comes when we reproduce to pass that genetic information down to the offspring.