DNA methylation

noun

: the enzymatically controlled addition of a methyl group to a nucleotide base (such as cytosine in eukaryotes) in a molecule of DNA that plays a role in regulating gene expression (as by the inhibition of genetic transcription)

When a methyl group attaches to a specific spot on a gene—a process called DNA methylation—it can change the gene's expression, turning it off or on, dampening it or making it louder.

—John Cloud

A handful of drugs that affect DNA methylation already exist, and are being used to treat cancers in which faulty gene labeling plays a role.

—Helen Pilcher

A process called DNA methylation sets down "marks" on bits of DNA and is typically thought to squelch gene expression.

—Sarah Baldauf

DNA methylation is a mark on genomic DNA made by addition of methyl groups to cytosine bases …

—Adrian Bird

Word History

First Known Use

1963, in the meaning defined above

Medical Definition

DNA methylation

noun

: the enzymatically controlled methylation of a nucleotide base (as cytosine in eukaryotes) in a molecule of DNA that plays a role in suppressing gene expression