Cytosine

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.

Cytosine
IUPAC name	4-amino-3H-pyrimidin-2-one
Identifiers
CAS Number	71-30-7
3D model (JSmol)	Interactive image
ECHA InfoCard	100.000.681
MeSH	Cytosine
PubChem CID	597
CompTox Dashboard (EPA)	DTXSID4044456
SMILES C1=C(NC(=O)N=C1)N
Properties
Chemical formula	C4H5N3O
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

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]