Answer:
Methionine and the enzyme DNA methyltransferase.
Step-by-step explanation:
DNA methylation is the process of addition of the methyl group at specific DNA site. The methylation is a type of epigenetic modification that can modify gene expression and its function.
The co factors that help in methylation are methionine, riboflavin and choline. They helps in the transfer of methyl group from one point to another. The enzymes like DNA methyltranferases adds the methyl group during the process of DNA methylation.