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. However, recall that DNA molecules actually exist predominantly as the double stranded form. So we have our double helix basically in DNA our two single strands of DNA align antiparallel and they hydrogen bonds to form our double helix. But the RNA exists predominantly in the single strand form and this is exactly what allows our RNA molecule to actually pass through the nuclear pores.