Epigenome

Article By:

Ortega-Recalde, Oscar Department of Anatomy, University of Otago, Dunedin, New Zealand.

Last reviewed:May 2021

DOI:https://doi.org/10.1036/1097-8542.238220

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• Epigenome, published July 2014:Download PDF Get Adobe Acrobat Reader

The complete set of epigenetic modifications possessed by an organism or an individual cell. Epigenetic modifications—that is, heritable changes of gene expression without any alteration of the genetic code itself—include (but are not limited to) DNA methylation (the addition of a methyl group to certain nucleotides in genomic DNA) and modifications of histones (small, positively charged proteins responsible for packaging the DNA of eukaryotic organisms). Unlike epigenetics, which is focused on individual genes, the epigenome refers to epigenetic modifications across the entire genome (the complete set of genetic material in an organism) [Fig. 1]. The term epigenetics was coined by Conrad H. Waddington in the 1940s. Over time, the concept of epigenetics was refined, and the term epigenetics is now defined as the branch of biology investigating heritable changes of gene expression and function that occur in the absence of DNA-sequence alterations. In general, epigenomic studies only became possible in the early twenty-first century with the development of methods enabling the collection of large volumes of epigenetic information, such as DNA microarrays and large-scale DNA sequencing. Accordingly, the scope of epigenetics has evolved since Waddington's original concept and now refers to the heritable modifications of DNA that allow cells to stably alter their gene expression patterns (to activate or repress). Importantly, these DNA modifications can be transmitted to offspring without requiring any underlying change in DNA sequence (epi, meaning "above or on top of"). See also: Deoxyribonucleic acid (DNA); DNA methylation; DNA microarray; Gene; Genetics; Genomics; Histone

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