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In cell biology a centriole (''centri-'' + ''-ole'') is a cylindrical cell structure composed mainly of a protein called tubulin that is found in most eukaryotic cells. An associated pair of centrioles, surrounded by a shapeless mass of dense material, called the pericentriolar material, or PCM, makes up a compound structure called a centrosome.〔 Centrioles are present in the cells of most eukaryotes, for example those of animals. However, they are absent from conifers (pinophyta), flowering plants (angiosperms) and most fungi, and are only present in the male gametes of charophytes, bryophytes, seedless vascular plants, cycads, and ginkgo. Most centrioles are made up of nine sets of microtubule triplets, arranged in a cylinder. Deviations from this structure include crabs and ''Drosophila melanogaster'' embryos, with nine doublets, and ''Caenorhabditis elegans'' sperm cells and early embryos, with nine singlets. Edouard van Beneden and Theodor Boveri made the first observation and identification of centrioles in 1883 and 1888 respectively, while the pattern of centriole duplication was first worked out independently by Etienne de Harven and Joseph G. Gall c. 1950 〔. See also de Harven's own recollections of this work: 〕 The main function of centrioles is to produce aster and spindle during cell division. ==Cell division== Centrioles are involved in the organization of the mitotic spindle and in the completion of cytokinesis. Centrioles were previously thought to be required for the formation of a mitotic spindle in animal cells. However, more recent experiments have demonstrated that cells whose centrioles have been removed via laser ablation can still progress through the G1 stage of interphase before centrioles can be synthesized later in a de novo fashion. Additionally, mutant flies lacking centrioles develop normally, although the adult flies' cells lack flagella and cilia and as a result, they die shortly after birth. The centrioles can self replicate during cell division. 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「Centriole」の詳細全文を読む スポンサード リンク
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