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Modern Genetic Analysis Chapter 15. Regulation of Cell Number: Normal and Cancer Cells
Introduction

In the last chapter, we learned about some ways in which a cell monitors its status relative to its environment and responds accordingly. For example, by utilizing certain metabolites as allosteric effectors of transcriptional regulatory proteins, an E. coli cell can make decisions about which sugar metabolic pathways to implement at any given time. Metazoa (multi-tissued animals) use steroids and other low-molecular-weight hormones as allosteric effectors of transcriptional regulatory molecules to coordinate appropriate responses of different organs to a particular physiological event.

A major point to remember is that cells have evolved mechanisms that modulate the activity of key target proteins by relatively minor modificationsin the two preceding examples, by forming complexes with allosteric effectors. Much of genetics, indeed much of the biology of a cell, depends on such modulations, in which key proteins are toggled between active and inactive states.

In this chapter and the next one, we shall see this theme exploited in a variety of situations: control of cell numbers, control of developmental pathways, and formation of complex biological patterns. In this chapter, we focus on how such modulations achieve proper control of cell number and how the systems can be overcome by certain classes of mutations to produce uncontrolled proliferationthe diseases that we call cancers.

© 1999 by W. H. Freeman and Company. All rights reserved.