Methyltransferases
Enzymes that move one methyl group onto a base
The sequence does not change. Who is allowed to act on it does.
Methyltransferases add a methyl group to a DNA base, most often the N6 of adenine or the C5 of cytosine. This is the smallest chemical event in the whole lecture, one carbon, and it is worth a section because of what it decides rather than what it is. A methylated site and an unmethylated site have identical sequence. Sequence the plasmid and you cannot tell them apart. What differs is which enzymes are allowed to act there. Think of methylation as an annotation layer sitting on top of the sequence. Section divider: Methyltransferases. Enzymes that move one methyl group onto a base. The sequence does not change; who is allowed to act on it does.