Name the two purine bases found in DNA.

The two purine bases found in DNA are adenine and guanine. They are nitrogen-containing bases with a two-ring chemical structure derived from the compound purine.

Adenine is represented by A and guanine by G. In normal DNA base pairing, adenine pairs with the pyrimidine base thymine, while guanine pairs with cytosine. This purine–pyrimidine pairing keeps the DNA double helix a consistent width.

Purines are not limited to DNA. Adenine and guanine also occur in RNA, where adenine pairs with uracil instead of thymine. They are also parts of important cellular molecules: ATP and GTP help power and regulate cellular activity, while related compounds participate in metabolism and signalling.

A common mix-up is to call all four DNA bases purines. Cytosine and thymine are pyrimidines, each built from a single ring. The purine–pyrimidine distinction describes chemical structure, not whether a base belongs to DNA or RNA.