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Structural inheritance or cortical inheritance is the transmission of an epigenetic trait in a living organism by a self-perpetuating spatial structures. This is in contrast to the transmission of digital information such as is found in DNA sequences, which accounts for the vast majority of known genetic variation. Examples of structural inheritance include the propagation of prions, the infectious proteins of diseases such as scrapie (in sheep and goats), bovine spongiform encephalopathy ('mad cow disease') and Creutzfeld-Jakob disease (although the protein-only hypothesis of prion transmission has been considered contentious until recently.) Prions based on heritable protein structure also exist in yeast. Structural inheritance has also been seen in the orientation of cilia in protozoans such as ''Paramecium'' and ''Tetrahymena'', and 'handedness' of the spiral of the cell in ''Tetrahymena'',〔 and shells of snails. Some organelles also have structural inheritance, such as the centriole, and the cell itself (defined by the plasma membrane) may also be an example of structural inheritance. To emphasize the difference of the molecular mechanism of structural inheritance from the canonical Watson-Crick base pairing mechanism of transmission of genetic information, the term 'Epigenetic templating' was introduced. ==History== Structural inheritance was discovered by Tracy Sonneborn, and other researchers, during his study on protozoa in the late 1930s. Sonneborn demonstrated during his research on Paramecium that the structure of the cortex was not dependent on genes, or the liquid cytoplasm, but in the cortical structure of the surface of the ciliates. Preexisting cell surface structures provided a template that was passed on for many generations. John R. Preer, Jr., following up on Sonneborn's work, says, "The arrangement of surface structures is inherited, but how is not known, Macronuclei pass on many of their characteristics to new macronuclei, by an unknown and mysterious mechanism." Other researchers have come to the conclusion that "the phenomena of cortical inheritance (and related nongenic, epigenetic processes) remind us that the fundamental reproductive unit of life is not a nucleic acid molecule, but the remarkably versatile, intact, living cell." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Structural inheritance」の詳細全文を読む スポンサード リンク
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