I thank many companies that have donated reagents, instrumentation, or supplies or granted generous educational discounts, including Promega, GlaxoSmith Kline, Merck, Amersham/Pharmacia, and Owl Scientific. I am indebted to the students of Molecular Biology, Biology 462 (1991 to present day), for their patience and hard work in the lab and for their helpful suggestions and comments. This project was based on and uses reagents derived from my research in the laboratory of Dr. F. Rob Jackson, whom I thank for his valuable training and for granting me the opportunity to teach a molecular biology course while still a postdoctoral researcher. I also thank Dr. Jay Moné for his helpful comments about this manuscript. Some of the equipment used in this investigation was provided in part by funding from National Science Foundation Instrumentation and Laboratory Improvement grants.