Do you know the difference between a Purine and a Pyrimidine?

Purines and Pyrimidines are the nitrogen-containing "bases" found in the nucleotides that make up DNA and RNA. As shown in Figure 12-5 from the Dragonfly Book (at right), purines have two rings in their structure, while pyrimidines have just one.

Unfortunately, while this Figure is correct in all editions of the book, early printings of the Dragonfly Book had a typographical error on Page 291 that reversed the identifications of these two types of bases. All printings of the book since June of 2002 should contain the corrected text.