chemical compound
IUPAC name 4-amino-3H-pyrimidin-2-one
  • 71-30-7
3D model (JSmol)
ECHA InfoCard 100.000.681
MeSH Cytosine
  • C1=C(NC(=O)N=C1)N
Molar mass 111.102
Melting point 320 - 325°C (decomp)
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Cytosine is one of the 5 main nucleobases used in storing and transporting genetic information within a cell in the nucleic acids DNA and RNA.

In DNA and RNA, cytosine is paired with guanine. However, it is unstable, and can change into uracil. This can lead to a point mutation if not repaired. The DNA repair enzymes, such as uracil glycosylase, cuts uracil in DNA.

Cytosine is the centre of modern genetic research into epigenetics. Methyl groups added to cytosine change the action of genes during lifetime. These changes are not inherited.[1]


  1. Carey, Nessa 2011. The epigenetics revolution: how modern biology is rewriting our understanding of genetics, disease and inheritance. London: Icon Books. ISBN 978-184831347-7

Other websites

  • Computational Chemistry Wiki Archived 2005-12-02 at the Wayback Machine
  • Shapiro R (1999). "Prebiotic cytosine synthesis: a critical analysis and implications for the origin of life". Proc. Natl. Acad. Sci. U.S.A. 96 (8): 4396–401. doi:10.1073/pnas.96.8.4396. PMC 16343. PMID 10200273.