Epigenetics is going to be the next great field in medicine.
Epigenetics is one thing. Copy number variation is quite another. It includes a range in the number of copies of a gene, from deletion, i.e. the absense of the gene altogether, to multiple copies of the same gene to different versions of a gene that makes a different, but functionally similar, protein, e.g. pancreatic amylase and salivary amylase. Click on the keywords copynumbervariation, copynumbervariations and cnv. It's not just simple Mendelian genetics and epigenetics.