שאלה | Some bases in DNA are occasionally methylated, typically C in eukaryotes and A in prokaryotes. This provides an additional ‘code’ to the information stored in DNA. How is this code maintained during DNA replication?

Some bases in DNA are occasionally methylated, typically C in eukaryotes and A in prokaryotes. This provides an additional ‘code’ to the information stored in DNA. How is this code maintained during DNA replication?

		1. It isn’t. The RNA polymerase holoenzyme has a demethylase activity. The methylation code is reset during DNA replication.
		2. Methyltransferases read the old strand and operate on the new strand.
		3. There is no need. Methylation is epigenetic. New methyl groups are added as needed depending on the environmental context.
		4. Since the methyl groups alter base-pairing, only correctly methylated bases will be used during DNA synthesis.