Cytosine residue in DNA (C (when referring to DNA sequence notation); otherwise, none in this context)

Cytosine is one of the four major nitrogenous bases (pyrimidine class, chemical formula C₄H₅N₃O) present in DNA, where it forms stable hydrogen bonds with guanine through Watson-Crick base pairing. In eukaryotic cells, cytosine residues in DNA can be methylated at the 5-position to form 5-methylcytosine, an epigenetic modification that plays critical roles in gene regulation, development, and disease. Aberrant modification or mutagenic deamination of cytosine contributes to genome instability and is implicated in carcinogenesis and other diseases

Other names

Cytosine base in DNADNA cytosine5-methylcytosine (for methylated forms)

Not applicable for cytosine residues directly\n(DNA methyltransferase inhibitors block methylation of cytosine residues in DNA, leading to changes in gene expression)