Ultimately, telomerase-deficient cells undergo replicative senescence, a process in which the majority of cells in the culture cease to grow, and a variety of deleterious genome-destabilizing events increase in frequency (Chen and Kolodner, 1999; Hackett et al., 2001; DuBois et al., 2002; Hackett and Greider, 2003; Mieczkowski et al., 2003; Meyer and Bailis, 2007).