Mnemonic for purine nitrogenous bases?

• A. CUT the PY
• B. PUR As Gold
• C. A and G
• D. Pyrimidines are two rings

Answer: (B)

Think about which bases are purines: those with two ring systems, specifically adenine and guanine. A mnemonic that fits this idea is "Pur As Gold" because it cues Purines and points to A and G as the bases that belong to this category. The other options don’t serve the purpose of a mnemonic for purines: one phrase actually reminds you of pyrimidines (the single-ring bases C, T, U), another option just lists A and G without forming a mnemonic, and one choice makes an incorrect claim about pyrimidines having two rings. So this mnemonic is the clearest, most direct way to remember which bases are purines.