methylation

https://doi.org/10.1351/goldbook.10954
Attachment of a methyl group to a molecule.
Note: Methylation of DNA on cytosine bases is an epigenetic event that alters gene expression.
Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 779 [Terms] [Paper]