Fig. 4.
Event rates are determined by a stochastic heritable change. (A) Blue bars: distribution of average event rates for individual colonies with [aTc] = 5 ng/mL; Ncolonies = 984. The mean rate of this distribution is 11.8 ± 12 × 10−3 events per cell per hour per colony. Red line: result of a two-step process simulated using the experimental distribution of colony sizes. Green line: result of a Poisson process with the mean rate of the experimental distribution. (Inset) Same data with logarithmic y axis. (B) Cartoon picture illustrating the Luria–Delbrück process used in our simulation where some fraction of cells inherit a trait that predisposes them to TE activity (red outline), and of those cells some fraction fluoresce blue, indicating TE activity (blue fill).