What We Do Not Know About Differentiation

The outstanding recent advances in the analysis of differentiationare in concept and method. In this paper examples are providedto demonstrate that formulation of the problem of differentiationin terms of biosynthesis and its control poses questions innew and more manageable ways. As examples, reference will bemade to: (1) the question of control of the sets of specializedproperties by which we define a cell type; (2) propagabilityof differentiated states; (3) developmental bias in relationto intracellular events; and (4) the mechanisms of extrinsiccontrol of differentiation. Particular attention, also, willbe focused on the relationship of morphogenetic to biosyntheticevents.