The regulation of gene expression in many biological processes involves epigenetic mechanisms. In this new volume, 36 chapters written by experts in the field discuss epigenetic effects from many perspectives. There are chapters on the basic molecular mechanisms underpinning epigenetic regulation, discussion of cellular processes that rely on this kind of regulation, and surveys of organisms in which it has been most studied. Thus, there are chapters on histone and DNA methylation, siRNAs and gene silencing; X-chromosome inactivation, dosage compensation and imprinting; and discussion of epigenetics in microbes, plants, insects, and mammals. The last part of the book looks at how epigenetic mechanisms act in cell division and differentiation, and how errors in these pathways contribute to cancer and other human diseases. Also discussed are consequences of epigenetics in attempts to clone animals. This book is a major resource for those working in the field, as well as being a suitable text for advanced undergraduate and graduate courses on gene regulation.