Why are cell populations maintained via multiple intermediate compartments?
Abstract: We consider the maintenance of a population of ``product'' cells from progenitor cells via one or more intermediate compartments. If there is only one intermediate compartment, a large ratio of product cells to progenitors can only be achieved at the cost of the product cell population being dominated by large families of cells descended from individual progenitors, and large average number of divisions separating product cells from progenitors. These undesirable features can be avoided if there are multiple intermediate compartments. A sequence of compartments is, in fact, an efficient way to maintain a product cell population from a progenitor population, avoiding excessive clonality and minimising the number of rounds of division ``en route''.