guanine
Meaning of guanine: Guanine is one of the four nucleobases in DNA and RNA, pairing with cytosine to help form the genetic code's structure.
Definition of guanine
Guanine is one of the four nitrogen containing bases that make up the genetic code carried in DNA and RNA, alongside adenine, cytosine, and, depending on the molecule, either thymine or uracil. Structurally, guanine belongs to a chemical group called purines, characterized by a double ring structure, which it shares with adenine.
Within the double helix of DNA, guanine pairs specifically with cytosine, the two bases held together by three hydrogen bonds, a pairing rule that underlies how genetic information is copied and read accurately. This same base pairing pattern also occurs wherever single stranded RNA molecules fold into paired structures.
Beyond its structural role in DNA and RNA, a related molecule built from guanine, guanosine triphosphate, serves as an energy source and signaling molecule used in many of the body's cellular processes.
Used in a sentence
Genetic sequencing identified a substitution at the guanine base within the gene of interest.
Good to know
Guanine's pairing with cytosine, rather than with adenine or thymine, is a fixed rule of DNA structure, and an error that disrupts this pairing is one mechanism underlying certain genetic mutations.