<Reviews>Clonal senescence in paramecium

概要

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The paramecium is a unicellular organism like a bacterium which reproduces freely under adequate culture conditions, but its cell clones do not divide in an unlimited fashion without sexual reproduction ; that is, a clonal life span clearly exists for the paramecium. To test the hypothesis that the clonal life span is limited by the accumulation of mutations in the macro-nucleus (which is the vegetative nucleus), we studied the effects of X-irradiation and lethal mutations on the clonal life span in Paramecium tetraurelia. X-irradiation accelerated the senescence of the cell clones and shortened the clonal life span. These results support the mutation theory. However, lethal mutations in the macronucleus were not necessarily responsible for shortening the clonal life span and the shortening rates were less than 40% in spite of an expected value of 67%. Because the structure of the macronucleus is not yet well understood, we can draw no conclusions from these data. Factors other than mutation in the macronucleus may have an important role in the clonal senescence of the paramecium.
近畿大学の論文