Changes

'''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>

'''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 inheritance 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 inheritance 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>https://www.ncbi.nlm.nih.gov/pubmed/19606595</ref><ref>https://www.ncbi.nlm.nih.gov/pubmed/19606595</ref>

Epigenetic silencing is also thought to provide a natural protection against [[retrovirus]]es 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.

Epigenetic silencing is also thought to provide a natural protection against [[retrovirus]]es 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.