Epigenetics is a term in biology referring to heritable traits that do not involve changes in the underlying DNA sequence of the organism. Epigenetic traits exist on top of or in addition to the traditional molecular basis for inheritance. The "epigenome" is a parallel to the word "genome," and refers to the overall epigenetic state of a cell. Cancer and stem cell research have gradually focused attention on these genome modifications. The molecular basis of epigenetics involves modifications to DNA and the chromatin proteins that associate with it. Methylation, for example, can silence a nearby gene and seems to be involved in some cancers.