Which of the functional groups is not reactive but serves as a recognizable tag on the dna molecule and alter the expression of genes in the cells?

Methyl functional group is a non-reactive but a recognizable tag on the DNA molecule and alter the expression of genes in the cells.

Methyl contains one carbon atom which is bonded to three hydrogen atoms. For example, CH3. Methyl group occurs in organic compounds and part of a larger molecule.

It can be found alone in the three forms which are cation, radical, and anion.