Correct Option: C

The addition of a methyl group (-CH₃) to a molecule is known as methylation. Extensive methylation of cytosine in DNA is correlated with reduced transcription. DNA methylation is one of several epigenetic mechanisms that cells use to control gene expression. Proteins can be methylated on the side-chain nitrogen of arginine and lysine residues or on carboxy-termini. Protein methylation is a way of subtly changing the primary sequence of a peptide so that it can encode more information. This common posttranslational modification is implicated in the regulation of a variety of processes including protein trafficking, transcription and protein-protein interactions.