ABSTRACT
The two main types of computer available, analogue and digital, reflect with remarkable fidelity two quite different approaches to the analysis of biological systems. This chapter considers somewhat superficially a particular biological phenomenon, the cycle of cell growth and division, in order to illustrate the two complementary aspects of the process and how they may be handled analytically by automata theory and by control theory. It suggests how these may be unified, and what problems are encountered in so doing. All cells experiencing a concentration above threshold differentiate into head cells, while these experiencing sub-threshold concentrations differentiate into stalk cells. A fundamental question in relation to control dynamics in cells is whether or not gene action has all-or-none character, a gene being full on when its repressor level is lower than a particular threshold value and shut off when it is above this value.
