1 DNA and RNA base pairing is slightly different, since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. 2  Uracil differs from thymine in that it lacks a methyl group on its ring. DNA is a double stranded molecule while RNA is a single stranded molecule. 2  DNA is stable under alkaline conditions while RNA is not stable. 3  DNA and RNA perform different functions in humans.