Irwin Whiting Sizer, a pioneer in molecular biology and champion of the recruitment of women and minority students, taught at MIT for over 60 years. He joined the MIT faculty in 1935 as an instructor in the Department of Biology and was named chair of the department in 1956, a position he held until 1967 when he was appointed dean of the graduate school. Sizer served as dean until 1976, when he returned to the Department of Biology as professor emeritus and instructor. He was instrumental in the development of many programs at MIT, including Whitaker College, the joint Ph.D. in oceanography at Woods Hole Oceanographic Institute, the Harvard-MIT Division of Health Sciences and Technology Program, and the introduction of interdisciplinary master’s degrees. Within the Department of Biology, he played a major role in the evolution of the biology curriculum from a classical program to a modern molecular biology program.