In RNA the adenine actually pairs with the uracil because we no longer have the thionine. So in RNA molecules. Our adenine pairs with your cell while the guanine pairs with our cytosine. Now what other differences exist between our DNA and RNA biological molecules? Well, another important difference between DNA and RNA is that RNA exists mostly as a single strand. So we do find double stranded RNA molecules but our RNA molecules predominantly exist in the single strand form.