What is DNA methylation?
DNA methylation is transfer of methyl group from SAM to Adenine or Cytosine. Therefore, this addition takes place on two DNA bases which are at Adenine and Cytosine.
DNA methylation is known as covalent modification which means it does not change sequence of DNA but affects the gene activity.
Thus is done by enzyme DNA methyltransferses or called as DNMTs
These DNMTs are of three types:
2. DNMT 3a
3. DNMT 3b
DNMT1 is used in maintenance of DNA methylation within the cell. It means it maintains the methylation from parent DNA strand to newly synthesised strand. DNMT 3a and DNMT 3b are required for de Novo methylation. They do not need hemi-methylated DNA, thus methy groups added to new positions.