Increased methylation of DNA

• Methylation is the addition of a methyl group (CH3) to a molecule. When DNA is methylated, the methyl groups are added to the cytosine bases.
• Methylation is able to inhibit the transcription of genes in two ways: by preventing the binding of transcriptional factors to the DNA, and also by attracting proteins that condense the DNA-histone complex (making the DNA inaccessible to transcription factors).