Methylation is a chemical modification of DNA and other molecules that may be retained as cells divide to make more cells. When found in DNA, methylation can alter gene expression. In this process, chemical tags called methyl groups attach to a particular location within DNA where they turn a gene on or off, thereby regulating the production of proteins that the gene encodes.
Methylation. Methylation is also used to identify different types of genomes. So for different bacteria, they methylate different sequences. Some bacteria will methylate the sequence GAATTC and that's how they recognize their own DNA versus foreign invading DNA. This methylation is also at the heart of how restriction enzymes are produced in a bacterial cell that don't then chop up that own cell's DNA but are used to recognize foreign DNA. That may be too complicated but that's what I think is interesting about methylation. It was really important for us for making YAC libraries. That's just my own little 2 cents.
Chief and NIH Distinguished Investigator
Translational and Functional Genomics Branch