Genome complexity: review of epigenetics studies (Introduction)

by David Turell @, Monday, December 07, 2015, 14:39 (3035 days ago) @ David Turell

This is a long article covering much of current research:-http://www.the-scientist.com/?articles.view/articleNo/44628/title/Ghosts-in-the-Genome/-"These and other model systems provide evidence that inheritable epigenetic information exists alongside the inheritable DNA sequence. In addition to RNAs and prion proteins, epigenetic information carriers include covalent modifications to nucleotides and histones, providing a wide variety of mechanisms that enable organisms to transmit information extragenomically. (See illustration above.) And the increasing acceptance of transgenerational epigenetics has, in turn, spurred renewed interest in the possibility that ancestral environmental conditions might influence the phenotypes of future generations.-"This idea, often referred to as the inheritance of acquired characters, was one aspect of Jean-Baptiste Lamarck's early evolutionary theories. But the current use of “Lamarckian inheritance” to refer to transgenerational epigenetic inheritance is something of a misnomer. In fact, the inheritance of acquired characters was hardly the defining feature of Lamarck's beliefs. His evolutionary theory did not include the basic concept of natural selection, and did not have a place for phenotypic variation existing prior to environmental challenges. Moreover, both Darwin and Lamarck believed that traits acquired in one's lifetime could be passed on. Famously, Darwin even developed a model of inheritance that invoked “gemmules,” which carried information from all parts of the body to alter the characteristics of the next generation.-"Today, a number of studies document a link between ancestral environmental conditions and changes in offspring behavior or metabolism, potentially validating some of the thinking of both seminal evolutionary theorists on this topic. It is now becoming clear that the environments of both the mother and the father can influence offspring phenotype.-***-"One way to experimentally probe the question of how a father transmits information to his offspring is to breed rodents using assisted reproductive technologies, such as artificial insemination or in vitro fertilization (IVF), that use purified sperm to fertilize ova. In the case of Nestler's social-defeat paradigm, IVF experiments using sperm from control or defeated male mice did not reproduce the effect in offspring, indicating either that the relevant paternal information is located outside of sperm (perhaps in the seminal fluid), or that the disruptive process of IVF and embryo culture might somehow prevent accurate transmission of sperm information to progeny. In contrast, in Diaz and Ressler's study pairing odorants with foot shocks, odor sensitivity was also affected in offspring generated via IVF using sperm from exposed versus unexposed male mice."-Comment: Many parts of the genome and the reproductive process can carry epigenetic information, including perhaps such items as seminal fluid!


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