Fig. 1. Cell cycles discussed at the meeting. Cell cycle phases can be modified to meet the demands of a cell at specific developmental stages. The first three cycles shown increase cell number by incorporating mitosis (M), but their coupling to external influences, such as growth, vary. In the fourth cycle shown, M is repressed, and the primary result of this is polyploidy, which is associated with growth and differentiation in many plant cell types and in some animal cell types.