Aneuploidy as a transient evolutionary step to adaptation

Aneuploidy, i.e. the change to a different number of chromosomes in single cells, occurrs quite frequently in nature. Prominent examples are human cancer cells and yeast populations under stress. We investigate if and under which conditions aneuploidy can facilitate local adaptation. We analyze both mathematical models and numerical simulations in which aneuploidy acts as a transient step towards a better adapted population. The main methods are based on the Wright-Fisher model and the theory of branching processes. One example for an important quantity that is derived, is the expected time until the population is successfully adapted. It depends heavily on the mutation rate, which is the rarest event that has to occur in order to achieve adaptation. This work can be seen as a first step towards establishing basic evolutionary theory for the process of aneuploidy as it seems currently to be lacking.