a) Damage level development.

<p>Cell populations that divide asymmetrically have a smaller average damage level and a higher fraction of cells with the initial damage level, compared to cells that divide symmetrically. When the number of undamaged cells fluctuates down to zero, the average damage level will quickly increase from the steady state value to 1, corresponding to a system collapse. This happens after a characteristic time . Parameters used: , , , . Other choices of parameters yield similar results. <b>b) Stability of steady state.</b> The time before system collapse decreases with the mutation probability and increases with higher mitochondrial fragility . Notably, cell populations that divide asymmetrically stay in steady state for much longer time than populations with symmetric division. White circles represent the set of parameters used in panel a.