The organic bases universally found in DNA and RNA . In a nucleotide sequence, a purine is often symbolized R, while a pyrimidine is symbolized by Y. The purines adenine and guanine occur in both DNA and RNA. The pyrimidine cytosine also occurs in both classes of nucleic acid. Thymine is found only in DNA, and uracil occurs only in RNA. See rare bases.
Bases of nucleic acids
Subjects: Genetics and Genomics.