 DNA methyltransferase

A DNA methyltransferase transfers a methyl group to DNA, commonly using S-adenosylmethionine as donor. Different enzymes modify different bases or sequence contexts. Some preserve an existing pattern after DNA replication, whereas others establish new marks. Consequently, unchanged sequence can coexist with altered DNA methylation and gene regulation; the modification changes chemical information on the inherited template rather than necessarily changing its base order. ^[ref]