Home Dna Test - The first three are the same as those found in DNA but in RNA thymine is replaced by uracil as the base complementary to adenine. This base is also a pyrimidine and is very similar to thymine. In DNA however uracil is readily produced by chemical degradation of cytosine so having thymine as the normal base makes detection and repair of such incipient mutations more efficient.
Thus uracil is appropriate for RNA where quantity is important but lifespan is not whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical.There are also numerous modified bases and sugars found in RNA that serve many different roles.
