What is "epigenetics"

n. 1 (context genetics English) The study of the processes involved in the genetic development of an organism, especially the activation and deactivation of genes. 2 (context genetics English) The study of heritable changes caused by the activation and deactivation of genes without any change in DNA sequence.

In the science of genetics, epigenetics is the study of cellular and physiological phenotypic trait variations that result from external or environmental factors that switch genes on and off and affect how cells express genes. Hence, epigenetic research seeks to describe dynamic alterations in the transcriptional potential of a cell. These alterations may or may not be heritable, although the use of the term epigenetic to describe processes that are heritable is controversial. Unlike genetics based on changes to the DNA sequence (the genotype), the changes in gene expression or cellular phenotype of epigenetics have other causes, thus use of the prefix epi- (Greek: επί- over, outside of, around).

The term also refers to the changes themselves: functionally relevant changes to the genome that do not involve a change in the nucleotide sequence. Examples of mechanisms that produce such changes are DNA methylation and histone modification, each of which alters how genes are expressed without altering the underlying DNA sequence. Gene expression can be controlled through the action of repressor proteins that attach to silencer regions of the DNA. These epigenetic changes may last through cell divisions for the duration of the cell's life, and may also last for multiple generations even though they do not involve changes in the underlying DNA sequence of the organism; instead, non-genetic factors cause the organism's genes to behave (or "express themselves") differently.

One example of an epigenetic change in eukaryotic biology is the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. In other words, as a single fertilized egg cell – the zygote – continues to divide, the resulting daughter cells change into all the different cell types in an organism, including neurons, muscle cells, epithelium, endothelium of blood vessels, etc., by activating some genes while inhibiting the expression of others.

Epigenetics is a monthly peer-reviewed scientific journal covering research pertaining to epigenetics. It was established in 2006 and published by Landes Bioscience, until this company was acquired by Taylor & Francis in 2014. It is the official journal of the Epigenetics Society (formerly the DNA Methylation Society). The editor-in-chief is Manel Esteller ( University of Barcelona).