n.
Organic compound of the purine family, often called a base, consisting of two rings, each containing both nitrogen and carbon atoms, and an amino group.
It occurs in combined form in many important biological molecules, particularly nucleic acids , and free or combined in various natural sources, including guano , sugar beets, yeast, and fish scales. In DNA its complementary base is cytosine . It or its corresponding nucleoside or nucleotide may be prepared from nucleic acids by selective techniques of hydrolysis .