X-Ray-Induced Division Delay of Individual Yeast Cells

The delay of cell division by sublethal doses of X-radiation has been extensively studied on a variety of tissues and cells; no attempt is made here to review all the literature on this subject. Considerable difficulty in interpretation has been inherent in many quantitative investigations of division delay by radiation when individual cells have not been followed. It has been the practice to determine mitotic index as a function of time after irradiation and to define the time required to reach some point on the curve, frequently the time at which the mitotic index reaches a minimum, as division delay. If subsidiary information is not available, this quantity then characterizes the effect of radiation on cells distributed in unknown fre-