Chemical structure of guanine, showing its double-ring purine structure and the functional groups involved in hydrogen bonding with cytosine. (Image: Public Domain) Guanine has the chemical formula ...
The purine structure consists of a pyrimidine ring (positions 1 to 6) fused to an imidazole ring (positions 7 to 9). Adenine and guanine, the two most common purines in DNA and RNA, share this core ...