The cell cycle—A cautionary note

Abstract Cell-cycle studies, largely conducted unsystematically in undefined conditions for growth in batch synchrony cultures, generally assume a fixed intrinsic pattern of behavior for the cell cycle that ignores the variable phenotypic activity of cells experienced in practice. However, cell-cycle studies conducted systematically in continuous cultures under defined growth conditions reveal a flexibility in cell performance. It is suggested that batch-synchrony studies should be conducted under several different growth conditions to establish the variability of their presently assumed fixed cell-cycle behaviors.