Epigenetic modifications act on DNA and its packaging proteins, the histones, to regulate genome function. Manifest as the heritable methylation of DNA and as post-translational histone modifications, these molecular flags influence the architecture and integrity of the chromosome, the accessibility of DNA to gene regulatory components and the ability of chromatin to interact within nuclear complexes. While a multicellular individual has only one genome, it has multiple epigenomes reflecting the diversity of cell types and their properties at different times of life; in health and in...