Animation of epigenetic tagging of DNA. The DNA molecule is seen in a coiled coil around histone proteins red, forming a densely_packed chromatin strand. The green light represents reading of the structure, which reveals the presence of inactivating epigenetic tags. Chemically this is typically accomplished by the methylation of the DNA. This turns off the affected gene. This is a heritable change in the DNA, one that can be transmitted to daughter cells during replication. The study of the heritable modification of gene expression is known as epigenetics.