Interphase Chromosomes

Abstract

Potu N. Rao did his graduate work on tobacco cytogenetics. In the 1950s and 1960s, job opportunities for plant cytogeneticists were extremely scarce, and many young botanical cytogeneticists turned to human cytogenetic, tissue culture, and related fields for survival and for new adventure. Potu was one of them. He joined Joseph Engelberg’s laboratory at the University of Kentucky, working on cell culture and cell physiology, using HeLa cells as the principal material. During these years, he developed expertise in cell synchronization, and discovered that nitrous oxide is a mitotic arrestant. HeLa cells, when blocked by colchicine at metaphase, have difficulty entering anaphase after the removal of colchicine from the culture medium, but they would divide normally after arrest by nitrous oxide. Rao also perfected the synchronization technique with an excess amount of thymidine to block the cells at the G₁-S border.