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A clone is a group of ''identical'' cells that share a ''common ancestry'', meaning they are derived from the same cell.〔(Clone definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms )〕 Clonality implies the state of a cell or a substance being derived from one source or the other. Thus there are terms like ''polyclonal''—derived from many clones; ''oligoclonal''〔(oligoclonal - Definition from Merriam-Webster's Medical Dictionary )〕--derived from a few clones; and, ''monoclonal''—derived from one clone. These terms are most commonly used in context of antibodies or immunocytes. ==Contexts== This concept of clone assumes importance as all the cells that form a clone share common ancestry, which has a very significant consequence: shared genotype. # One of the most prominent usage is in describing a clone of B cells. The B cells in the body have two important phenotypes (functional forms) -- the antibody secreting, terminally differentiated (that is, they cannot divide further) plasma cells, and the memory and the naive cells—both of which retain their proliferative potential. # Another important area where one can talk of "clones" of cells is neoplasms.〔(Clonal Origin and Expansions in Neoplasms: Biologic and Technical Aspects Must Be Considered Together - Pozo-Garcia et al. 162 (1): 353 - American Journal of Pathology )〕 Many of the tumors derive from one (sufficiently) mutated cell, so they are technically a single clone of cells. However, during course of cell division, one of the cells can get mutated further and acquire new characteristics to diverge as a new clone. However, this view of cancer onset has been challenged in recent years and many tumors have been argued to have polyclonal origin,〔Many different tumor types have polyclonal tumor origin: evidence and implications. Parsons BL. 659(3):232-47 - Mutation Research〕 i.e. derived from two or more cells or clones, including malignant mesothelioma.〔(Clonal Evaluation of Malignant Mesothelioma ). Comertpay et al. 2014 12:301 - Journal of Translational Medicine. doi: 10.1186/s12967-014-0301-3〕 # All the granulosa cells in a Graafian follicle are in fact a clone. # Paroxysmal nocturnal hemoglobinuria is a disorder of bone marrow cells resulting in shortened life of red blood cells, which is also a result of clonal expansion, i.e., all the altered cells are originally derived from a single cell, which also somewhat compromises the functioning of other "normal" bone marrow cells. 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「Clone (cell biology)」の詳細全文を読む スポンサード リンク
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