Epigenetic processes, which do not change the sequence of the DNA itself, are known to modify the way genes are expressed during development. They include DNA methylation, histone modifications and RNA interference, all processes that are associated with changes in chromatin conformation. Recent research into the contribution of epigenetics to the differential regulation of gene expression, imprinting (where expression depends on the parent-of-origin), gene silencing, and the involvement of transposable elements in these processes, have all shed fresh light on the relationships between genotype and phenotype. These processes could lead to the onset of diseases in adulthood, including some tumours. In this special issue, we provide a selection of reviews that covers epigenetic processes occurring at several different levels, and in various organisms.
