CORRELATION IN G1 TRANSIT-TIME OF SISTER CELLS SYNCHRONIZED BY MITOTIC SELECTION

Chinese hamster ovary (CHO) cells synchronized by mitotic selection were monitored by [3H]TdR autoradiography for entry into S phase. Consistent with the transition probability model of cell cycle control [1], the percent of cells remaining in G1 vs time (plotted on semi-log scale) appears linear after a slight initial curve. Analysis of the labeling pattern of sister cells indicates the following. 1. 1. The labeling index, determined from scoring only cells distinguishable as sister pairs, is the same as that for the total population; 2. 2. the proportion of pairs in which one sister is labeled is less than that expected if labeling is random, while the proportion of pairs in which both sisters are labeled is greater than that expected if labeling is random. These results indicate either exit from a hypothetical A state is not random, and/or transit through G1 subsequent to exit from the A state results in significant correlation of sister cell transit time. © 1979.