| 释义 |
episome Genetics.|ˈɛpɪsəʊm|
[f. epi- + -some4.]
a. A small particle which together with a larger ‘protosome’ was postulated to constitute a gene, and which by its absence was held to cause gene mutation. (No longer current.)
1931D. H. Thompson in Genetics XVI. 268 The gene [is pictured] as consisting of a main particle firmly anchored in the chromosome with varying numbers of one or more kinds of other particles attached. The main particle is called the protosome and the attached particles the episomes. 1966E. A. Carlson Gene xiii. 111 Using the position effect hypothesis with Thompson's protosome-episome chain theory of the gene, Dobzhansky tried to account for the various Bar mutations and their reversions.
b. [ad. F. épisome (Jacob and Wollmann 1958, in Compt. Rend. CCXLVII. i. 154).] A particle sometimes found in cells, esp. in bacteria, which has a genetic function and which can either exist and multiply as an independent unit or become attached to a chromosome and multiply with it. Hence epiˈsomal a., pertaining to or having the character of an episome; epiˈsomally adv., by means of or as a result of episomes.
1960Bacteriol. Rev. XXIV. 209/1 For genetic factors that are additions to..the genome,..Jacob and Wollman..have proposed the term ‘episomes’. 1962New Scientist 6 Sept. 514/3 An episome is a genetically active particle which can exist in two alternative forms. Ibid., These ideas have led Jacob and Wollman to propose the ‘episome’ hypothesis of extra-chromosomal inheritance. Some examples of episomally controlled inheritance..would be those controlling non-essential cell functions. Ibid., The episomal determinants of bacteria. 1965Times 26 Feb. 15/4 They are known collectively as episomes, a term which conveys merely that they are particles additional to the chromosome. 1968J. A. Serra Mod. Genetics III. xix. 24 Certain properties in bacteria are transmitted by the type of particle called an episome. Ibid. xxiii. 643 Variable location of the sex locus is better explained in terms of transposition of an episomal element, as in the dipteran Megaselia scalaris. |