The book builds from the basic relationship between promoters, operators and repressors that is at the heart of the decision between bacteriophage lambda's two lifestyles, lysis and lysogeny.
The account expands to include a brief discussion of other regulatory mechanisms that govern the expression of lambda's genome. It then goes on to extrapolate from these mechanisms to possible developmental decisions made in eukaryotic cells. Lambda, as we lambdologists always suspected, could be the genetic homunculus in all "higher" life forms.
Ptashne begins by presenting the current model of gene expression that he and his colleagues have unraveled so successfully. The reader needs no prior knowledge of the subject, for Ptashne gives all essentials along the way. He describes the structure of DNA in relation to the repressor and polymerase proteins that bind to it and discusses the subtleties of such bindings and interactions. He shows the repressor protein, known by its amino acid sequence as well as its three-dimensional structure, in its precise molecular relationship to DNA and explains the effects of these molecular relationships on the control of gene function.
Only after the total scheme is well in hand do we go back 40 years to retrace clearly the experimental work that led to the current model. Deductions from genetic, kinetic, chemical and molecular experiments are integrated and include references to the original publications.
All this is made visible by a wealth of drawings remarkable for their clarity. The drawings model the operations of experimental procedures, the arrangements of genetic units and the interactions of molecules. The figures are perfectly juxtaposed to the text, giving constant visual reinforcement of the concepts being discussed.
A Genetic Switch succeeds in giving a complete and current account of the molecular interactions that govern the on and off states of the best known regulator of gene expression. Without omitting details, the book makes the sophisticated molecules seem simple and accessible to all. The book lacks (for the sake of brevity) only a sense of the intrigue of research, of the way experiments are conceived to test preconceptions and of the intuitive jumps to new conceptions.
Phage lambda played no small part in the development of molecular genetics: volumes have been written on it. Therefore, a clear and engaging introduction that has up-to-the-minute scientific accuracy will surely find a niche and serve as a springboard for the next generation.