[ sahy-tuh-seen, -zeen, -sin ]
/ ˈsaɪ təˌsin, -ˌzin, -sɪn /

noun Biochemistry.

a pyrimidine base, C4H5N3O, that is one of the fundamental components of DNA and RNA, in which it forms a base pair with guanine. Symbol: C

Origin of cytosine

< German Cytosin (1894); see cyto-, -ose2, -ine2 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for cytosine


/ (ˈsaɪtəsɪn) /


a white crystalline pyrimidine occurring in nucleic acids; 6-amino-2-hydroxy pyrimidine. Formula: C 4 H 5 N 3 OSee also DNA, RNA
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

Medicine definitions for cytosine


[ sītə-sēn′ ]


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

Science definitions for cytosine


[ sītə-sēn′ ]

A pyrimidine base that is a component of DNA and RNA, forming a base pair with guanine. Chemical formula: C4H5N3O.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.