font size

Definition of Methylation

Methylation: 1. In chemistry, the addition of a methyl group to a molecule. 2. On a protein level, the addition of a methyl group or groups to the amino acid arginine or lysine in a protein. 3. On a DNA level, the addition of a methyl group to a cytosine residue to convert it to 5-methylcytosine. Methylation of DNA occurs at CpG sites, where cytosine (C) lies next to guanine (G). The CpG sites are in regions near the promoters of a genes. These regions are known as CpG islands. The state of methylation of CpG islands is critical to both gene activity and gene expression.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=26387
Last Editorial Review: 6/14/2012

Drug Medical Dictionary of Terms by Letter

Top RxList Drug News

Women's Health

Find out what women really need.

advertisement
advertisement
Use Pill Finder Find it Now See Interactions

Pill Identifier on RxList

  • quick, easy,
    pill identification

Find a Local Pharmacy

  • including 24 hour, pharmacies

Interaction Checker

  • Check potential drug interactions
Search the Medical Dictionary for Health Definitions & Medical Abbreviations