The term epigenetics refers to changes that involve the genetic material and lead to phenotypic changes but do not alter the DNA sequence. Epigenetic changes mainly include the methylation of DNA and modifications of chromatin like methylation and acetylation of the histones, the DNA’s packaging material. Epigenetic changes are acquired during the life of an organism and they are important for gene regulation, with big differences observed in epigenetic marks across different tissues. Environmental factors can also influence epigenetic marks through life, before they are reprogrammed in gametogenesis and early embryogenesis (42). Occasionally epigenetic changes can escape reprogramming and be vertically transmitted across generations and as a result an acquired epigenetic state can persist in the next generation, in other words it can be inherited. The involvement of epigenetic modifications in cancer is well known (43) and their potential importance in complex diseases has been argued by many (44–46), and it has been suggested that such epigenetic changes could be a source of missing heritability (22). Although this view has been challenged (47) it is clear that epigenetic variation can
