Epigenetics is the study of changes in gene function that are heritable and cannot be attributed to alterations in the DNA sequence. The term epi means above. It is a Greek prefix. It is also defined as above the base DNA sequence. In general terms it can be compared to word accents where the DNA is the language, and the modifications are the accents. Epigenetic marks change the way genes are expressed. It tells us about the cell, it is a way of defining the cell that is different than if we simply look at gene expression levels. Any type of cell that we look at has specialised epigenetic patterns.