The four bases that make up this code are adenine (A), thymine (T), guanine (G) and cytosine (C). Bases pair off together in a double helix structure, these pairs being A and T, and C and G. RNA doesn’t contain thymine bases, replacing them with uracil bases (U), which pair to adenine1.Click to see full answer. Regarding this, how many bases does RNA have? four Likewise, which is found in both DNA and RNA? The bases adenine, guanine, and cytosine are found in both DNA and RNA; thymine is found only in DNA, and uracil is found only in RNA. Secondly, what are the base pairing rules for DNA and RNA? DNA and RNA bases are also held together by chemical bonds and have specific base pairing rules. In DNA/RNA base pairing, adenine (A) pairs with uracil (U), and cytosine (C) pairs with guanine (G).Why is RNA unstable?RNA is susceptible to alkaline hydrolysis because the ribose sugar in RNA has a hydroxyl group at the 2′ position, which makes RNA chemically unstable compared to DNA (DNA has hydrogen at the 2′ position). DNA is stable in alkaline conditions. The RNA base, uracil, lacks this methyl group.