DNA methylation

DNA methylation is the covalent addition of methyl groups to DNA, most commonly to cytosine bases in vertebrates. It can influence gene activity without changing the DNA sequence.

DNA methyltransferase: An enzyme that transfers a methyl group to DNA, usually onto cytosine. These enzymes install methyl marks on DNA.
Cytosine: A pyrimidine nucleobase found in DNA and RNA. It is the principal DNA base that receives methyl groups in mammals.
Bisulfite sequencing: A sequencing method that distinguishes unmethylated cytosines from most methylated cytosines through bisulfite conversion. It maps DNA methylation at individual-base resolution.
DNA demethylation: The removal or chemical reversal of methyl groups attached to DNA. It opposes methylation and can restore activity at regulated regions.
X-chromosome inactivation: The chromosome-wide silencing of one X chromosome in cells of female mammals. DNA methylation helps maintain silencing of the inactive X.
DNMT1: A DNA methyltransferase that preferentially copies methylation patterns onto newly replicated DNA. It helps preserve methylation after DNA replication.
5-methylcytosine: A modified cytosine carrying a methyl group at carbon 5 of its ring. This is the predominant methylated DNA base in vertebrates.
DNA methylation array: A microarray assay that measures methylation at selected genomic CpG sites. Arrays provide a scalable way to compare methylation profiles.
Histone methylation: The addition of methyl groups to histone proteins, which can either activate or repress genes. It modifies chromatin proteins rather than DNA bases.
Transposable element: A DNA sequence capable of moving or copying itself to new locations in a genome. Methylation suppresses many transposable elements and limits their activity.

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