A Method for Improving Synchrony in the G2 Phase of the Cell Cycle

Presently available techniques for synchronizing by selective detachment of mitotic cells from mammalian cells allow the preparation and anal- monolayers (Robbins and Marcus, 1964; Robbins ysis of populations in the mitotic, G1, and S and Scharff, 1966) or by exposure of random phases of the cell cycle. However, synchronization cells to 2 mm thymidine (Xeros, 1962; Bootsma 942 THE JOURNAL OF CELL BIOLOGY • VOLUME 49, 1971 • pages 942-945et al., 1964) yields populations which lose their synchrony by the time they reach the G2 phase, and therefore systematic study of the morphological and biochemical events which immediately precede mitosis has been seriously hampered. In this report we describe a combination of existing methods which provides a population with improved synchrony in G 2. MATERIALS AND METHODS Stock suspension cultures of HeLa cells (S3 strain) were maintained at between 2 and 4 X 10 6 cells/ml