DNA methylation plays a significant role in the expression of the genetic code 
and affects early growth and development through its influence on gene 
expression. DNA methyltransferase 1 (Dnmt1) is the enzyme responsible for 
maintaining the methylation marks through cell division. However, the de novo 
methyltransferases, Dnmt3a and Dnmt3b, can also contribute to the maintenance of 
the methylation pattern. Manipulation of these enzymes, especially Dnmt1, 
provides a means to alter DNA methylation levels. Manipulation of the DNA 
methylation pattern of somatic cells will allow a better understanding of the 
different molecular process associated with chromatin structure and gene 
expression. Different approaches to artificially manipulate the expression of 
Dnmt1 in somatic cells include the addition of 5-azacytidine, culture of cells 
for an extended period of time, and the use of small interfering RNA 
technologies.