Fig. 1

Telomerase inactivation leads to increasingly frequent cell cycle arrests. A Median cell cycle duration of cells from individual lineages as a function of generations in telomerase-positive cells (n = 2418 cell cycles). Gray lines represent the 1st and 3rd quartile. Generation count begins with image acquisition. B Same as A but in telomerase-negative lineages (n = 12,903 cell cycles). Generation count starts with telomerase inactivation. C Scheme depicting two types of telomerase-negative lineages: (upper panel) the first arrest can be followed later on by at least one cell cycle of normal duration and is therefore “non-terminal”, or (lower panel) the first arrest can initiate the limited number of successive arrests characteristic of senescence and thus is “terminal”. D Cumulative distribution of the first appearance of terminal (red) and non-terminal (blue) arrests, with threshold D = 180 min