Epigenetic Mechanisms (IMAGE) Deutsches Zentrum fuer Diabetesforschung DZD Caption DNA methylations occur when methyl groups bind to the DNA. These can either activate or inactivate genes. Epigenetic factors modify histone tails by e.g. transferring methyl or acetyl groups on lysine side chains. This can complicate or facilitate the activation of a gene. The direct methylation of the DNA changes the gene expression permanently if it takes place in the control regions of genes (so-called CpG islands), that have been made accessible by the modification of the histones. Credit Copyright: DIfE Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.