Dictionary of Human Evolution and Biology

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Supermethylation

Addition of methyl groups to cytosine bases (usually at CpG dinucleotides). The extra methyl groups can inactivate a gene’s promoter region, causing an effect similar to mutation in the structural portion. Supermethylation has been implicated in 20-50% of women with certain breast cancers but without a mutated BRCA1 gene.

See DNA methylation.