What does demethylation mean?
Demethylation is the removal of a methyl group — a small carbon-and-hydrogen unit (-CH3) — from a molecule. The term belongs chiefly to chemistry and biology. In organic chemistry, demethylation describes reactions that strip methyl groups from compounds such as ethers or amines, often to transform one substance into another. Its most prominent modern use, however, is in molecular biology and epigenetics, where it denotes the erasure of methyl marks from DNA or from histone proteins around which DNA is wound. Because methylation of DNA generally suppresses gene activity, demethylation frequently has the effect of switching genes back on; large-scale demethylation shortly after fertilisation helps reset the embryo's genetic programme. Writers distinguish active demethylation, carried out directly by enzymes, from passive demethylation, in which methyl tags are progressively diluted as DNA replicates. The word appears mainly in academic, medical, and biotechnological prose rather than everyday speech.
nounThe chemical process of removing a methyl group (-CH3) from a molecule. In biology, it refers especially to the removal of methyl groups from DNA, which can activate gene expression.
- In chemistry: the removal of one or more methyl groups from a molecule.
- In molecular biology and epigenetics: the removal of methyl groups from DNA or from histone proteins, often altering gene expression.
"DNA demethylation at the promoter region allowed the previously silenced gene to be expressed again."
"Global DNA demethylation occurs shortly after fertilisation as the embryo resets its epigenetic state."
"The enzyme catalysed the demethylation of the aromatic substrate under mild laboratory conditions."
Rarely pluralised; usually treated as an uncountable process noun, though 'demethylation events' is common in scientific writing.
"Multiple demethylations across the genome reshaped the cell's expression profile."
Flip a single methyl 'tag' off your DNA and a silent gene can switch back on — demethylation is literally how cells rewrite their own instruction manual.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of demethylation
Demethylation is built transparently from Greek- and French-derived parts: the prefix de- (from Latin, meaning removal or reversal), methyl (coined in the 19th century by chemists combining Greek methy, 'wine', with the suffix -yl), and the noun-forming suffix -ation. The underlying element methyl entered English through German chemical nomenclature in the 1830s–40s. As chemists developed terms for adding and removing alkyl groups, demethylation arose naturally alongside methylation within late 19th- and 20th-century chemistry, later extending into molecular biology with the discovery of DNA methylation and its enzymatic reversal.
Related word forms
How demethylation is actually used
A technical term used almost exclusively in scientific and academic contexts — chemistry, biochemistry, genetics, and medicine. It is neutral in connotation but in biomedical writing it often carries an implication of gene activation, since removing methyl tags from DNA typically permits transcription. In epigenetics, writers distinguish active demethylation (enzyme-driven) from passive demethylation (dilution across rounds of replication).
Easily confused with demethylation
Methylation is the addition of a methyl group to a molecule, whereas demethylation is its removal — opposite directions of the same biochemical reaction.