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 ...

Comparison of a single-stranded RNA and a double-stranded DNA with their corresponding nucleobases. (Image: Wikimedia Commons, CC SA 3.0) The most common type of base pairing is the Watson-Crick base ...