The Age Structure of Populations of Cells Reproducing by Asymmetric Division

The purpose of this paper is to present a new model for the growth and age structure of a population of a species which reproduces by asymmetric division, i.e. cell reproduction where one clearly can distinguish between the mother and the daughter cell after division as opposed to division patterns where each fission produces two equal daughter cells. The cells of such populations are thus naturally divided into different classes according to the number of divisions they have undergone. A typical example of an organism which divides asymmetrically is Sacehavomyees oevevisiae, which reproduces by budding. After each cell separation a bud scar is left on the wall of the mother cell. These scars can be counted using electron microscopy. We say that a cell with i offsprings and hence i bud scars belongs to the ith scar class. It is supposed that cells of different scar classes behave in a different way, for instance with respect to cell growth and metabolism activity.