Methylation was initially addressed as one of the most primitive mechanisms that organisms utilize to (a) protect genomic DNA and initiate the host resistance mechanism towards foreign DNA insertion and subsequently, (b) control gene expression, (Doerfler & Böhm, 2006). From an evolutionary point of view as well, the catalytic domain in the structure of the methylation enzymes across all organisms has been preserved to perform methyl group addition. A major change however, in the level and functional utility of DNA methylation was noted in higher organisms such as eukaryotes, when DM mechanism evolved from protecting the genomic contents to controlling their level of gene expression. In humans, there.
