Epigenetics is the study of heritable change in gene activity despite alteration of the hosts DNA sequence. Change in gene activity done independently of the DNA sequence is achieved by way of histone and DNA methylation. Gene silencing in DNA methylation is carried out by DNA methyltransferases 1, 2 and 3a/b (DNMT1, DNMT2, DNMT3A/B). On a broad level, DNMTs methylate the fifth carbon of cytosine residues in DNA within CG dinucleotides.
