cdc45-10 and dpb11-10 mutants accumulate Okazaki-sized DNA fragments. (A) Exponentially growing rho° cultures, continuously labeled with 14C-uracil, were shifted to 35°C, and 3H-uracil was added for 30 minutes (left panels) or 90 minutes (right panels). The DNA was fractionated in alkaline sucrose gradients. Sedimentation is from left to right (fraction 1 is the top). φX174 and λ DNA migrated to fractions 6 and 11, respectively. Acid precipitable 3H (■) and 14C (○) cpm are plotted as the percent total cpm. Each graph is the average of at least three experiments. (B) The relative accumulation of Okazaki-sized DNA fragments (fractions 1–7) or full length DNA molecules (fractions 14–20) at 35°C was assessed by summing the percentage of 3H cpm in the top, middle, and bottom portions of each gradient and subtracting the percentage of 14C cpm obtained with continuous labeling at 26°C. Results from the 30-minute 3H gradients are gray, and those from 90-minute 3H gradients are white. Values >0 indicate an accumulation of 3H label at 35°C whereas values <0 indicate a deficit.