noun Biochemistry.

a purine base, C5H5N5O, that is a fundamental constituent of DNA and RNA, in which it forms base pairs with cytosine. Symbol: G

Compare guanosine.

Origin of guanine Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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Historical Examples of guanine

British Dictionary definitions for guanine



a white almost insoluble compound: one of the purine bases in nucleic acids. Formula: C 5 H 5 N 5 O

Word Origin for guanine

C19: from guano + -ine ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for guanine

1850, from guano, from which the chemical first was isolated, + chemical suffix -ine (2).

Online Etymology Dictionary, © 2010 Douglas Harper

guanine in Medicine




A purine base that is an essential constituent of both RNA and DNA.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

guanine in Science



A purine base that is a component of DNA and RNA, forming a base pair with cytosine. It also occurs in guano, fish scales, sugar beets, and other natural materials. Chemical formula: C5H5ON5.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.