Epigenetics
In biology, and specifically genetics,
epigenetics is the study of heritable changes in gene activity that are
not caused by changes in the DNA sequence; it also can be used to describe the study of stable, long-term alterations in the transcriptional potential of a cell that are not necessarily heritable. Unlike simple genetics based on changes to the DNA sequence, the changes in gene expression or cellular phenotype of epigenetics have other causes, thus use of the term
epi- -genetics. In plainer language, epigenetics is the study of changes in the expression of genes caused by certain base pairs in DNA, or RNA, being "turned off" or "turned on" again, through chemical reactions. 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.