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expanded article, still a work in progress
'''Epigenetics''' is the study of the heredity of variations in [[gene]] [[gene regulation|regulation]] and, thus, [[phenotype]], that occurs independent of any change in [[DNA]] sequence. The primary mechanism by which this happens is through [[post-translational modifications|post translational modification]] (e.g. methylation and acetylation) of [[histones]], although several other mechanisms are known to exist. Epigenetic gene regulation is also important physiologically; epigenetic reprogramming is one of the major mechanisms by which [[pluripotent stem cells]] and, subsequently, their daughter cells are committed to a specific [[list of cell types|cell type]] lineage during [[developmental biology|development]].
'''Epigenetics''' is the study of the heredity of variations in [[gene]] [[gene regulation|regulation]] and, thus, [[phenotype]], that occurs independent of any change in [[DNA]] sequence. The primary mechanism by which this happens is through [[post-translational modifications|post translational modification]] (e.g. methylation and acetylation) of [[histones]], although several other mechanisms are known to exist. Epigenetic gene regulation is also important physiologically; epigenetic reprogramming is one of the major mechanisms by which [[pluripotent stem cells]] and, subsequently, their daughter cells are committed to a specific [[list of cell types|cell type]] lineage during [[developmental biology|development]]<ref>Strachan & Read (2004). ''Human Molecular Genetics''.</ref>.
Epigenetic inheretance allows for more dramatic and rapid phenotypic change withinin populations across generations, and thus more rapid [[adaptation]] to environmental change, than random [[mutation]] alone. In some species, certain traits are known to be on a sort of epigenetic "on/off switch" (e.g. the presence or absence of protective spines in ''Raphanus raphanistrum'', the wild radish), where they can be activated or deactivated between generations in response to environmental challenge<ref>http://www.annualreviews.org/doi/full/10.1146/annurev.genom.9.081307.164445</ref><ref>http://www.ncbi.nlm.nih.gov/pubmed/19606595</ref><ref>http://www.ncbi.nlm.nih.gov/pubmed/19606595</ref>.
Epigenetic silencing also thought to provide a natural protection against [[retrovirus|retroviruses]] and inappropriate activation of [[transposons|transposable DNA elements]] (segments of DNA that move around in the genome)<ref>Simmen et al. (1999). Nonmethylated transposable elements and methylated genes in a chordate genome. ''Science'' 283, 1164-1167.</ref>. Although, the precise nature of this role is still somewhat disputed and remains an active area of research.
However, the most important role of epigenetic gene regulation, by far, is in differential [[gene regulation]] during [[developmental biology|development]], where epigenetic reprogramming is a major regulator of [[cell differentiation]].
==References==
<references/>