DNA methylation plays an important role in normal organismal development and in cellular differentiation in higher organisms. Gene expression, as well as the development of nearly all types of cancer, are also tied to DNA methylation. For example, global decrease in 5-methylcytosine content (DNA hypomethylation) is likely caused by methyl-deficiency due to a variety of environmental influences, and has been proposed as a molecular marker in multiple biological processes such as cancer. Global quantification of DNA methylation is crucial for understanding the roles that gene expression and silencing play in the development of cancer and other diseases.