A Safety Considerations Many techniques described here involve a number of hazards, such as high electrical current and voltage, radioactivity and highly toxic chemicals. It is absolutely essential that the instructions of equipment manufacturers be followed, and that particular attention be paid to the local and federal safety regulations. B Introduction The expression of prokaryotic and eukaryotic genes has been shown most often to be regulated at the level of mRNA synthesis. Thanks to the rapid development of methods for dissecting DNA sequences, cis-acting regulatory elements such as...