LACK OF TELOMERE SHORTENING DURING SENESCENCE IN PARAMECIUM

Paramecium tetraurelia cells have a limited clonal life span and die a fter approximate to 200 fissions if they do not undergo the process of autogamy or conjugation. To test the possibility that cellular senesc ence of this species is caused by telomere shortening, we analyzed the genomic DNA of the macronucleus during the clonal life span of P. tet raurelia. We found that telomeric DNA sequences were not shortened dur ing the interval of decreased fission rate and cellular death, defined as senescence in these cells. However, the mean size of the macronucl ear DNA was markedly decreased during the clonal life span. We present a model that expands upon previous proposals that accumulated DNA dam age causes cellular senescence in P. tetraurelia.