  The asymmetrical inheritance of plasmid DNA, as well as other cellular
components, has been shown to be involved in replicative aging. In
Saccharomyces cerevisiae, there is an ongoing debate regarding the mechanisms
underlying this important asymmetry. Currently proposed models suggest it is
established via diffusion, but differ on whether a diffusion barrier is
necessary or not. However, no study so far incorporated key aspects to
segregation, such as dynamic morphology changes throughout anaphase or plasmids
size. Here, we determine the distinct effects and contributions of individual
cellular variability, plasmid volume and moving boundaries in the asymmetric
segregation of plasmids. We do this by measuring cellular nuclear geometries
and plasmid diffusion rates with confocal microscopy, subsequently
incorporating this data into a growing domain stochastic spatial simulator. Our
modelling and simulations confirms that plasmid asymmetrical inheritance does
not require an active barrier to diffusion, and provides a full analysis on
plasmid size effects.
