Common DNA modifications occur through methylation, a chemical process that can dramatically change gene expression, which regulates the eventual production of proteins that carry out the functions of an organism.
DNA encodes genetic information in its chemical bases: adenine, cytosine, guanine, and thymine. Methylated cytosine is the dominant DNA modification found in eukaryotes, a taxonomical classification that includes mammals, insects, worms, plants, and algae, but new papers have identified an adenine DNA methylation that also epigenetically regulates cellular function in green algae, worms, and flies.