Glossary

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DNA methylation

A natural regulatory process in the cell, which controls gene activity

Special enzymes known as methyltransferases transfer a methyl group (CH₃ group) to the DNA building block cytosine at specific sites in the genome to produce methylcytosine. When this process affects regulatory DNA segments, it modifies the ‘readability’ of a gene. The conversion of cytosine is reversible.

The methylation of DNA bases has various biological functions. In bacteria, methylation is used to mark the bacteria’s own DNA (to distinguish it from foreign DNA) and is involved in error correction in DNA synthesis.

In higher organisms, methylation is used to mark active and inactive regions of DNA.

Since DNA methylation affects the transcription of genetic information without changing the DNA sequence itself, it is one of the principal mechanisms of epigenetics.