Genome-wide cytosine methylation studies are an example. These studies are based on the sensitivity of certain restriction enzymes to cytosine methylation and the relative resistance of methyl cytosine to disulfide-induced deamination.
Restriction landmark genome scanning (RLGS), a classic example of cytosine methylation, uses a rare-cutting methylation sensitive restriction enzyme together with another enzyme to create a profile of Notldigestion products. Digested Notloverhanging ends are radiolabelled and separated by a two dimensional gel electrophoresis. This technique can resolve about 2,000 sites. MALDI-TOF is enzyme-based technique with high-throughput bisulfate sequencing. It is the technique behind the European Human Genome Project. It is important to note that most of the techniques that use enzymes and methylation differ in terms of how they detect the genomic source of the distinctive fractions and how they select the fraction of the genomes (Jason, D., et al, 2006).