Figure 3.

In the absence of UvrD, the nascent DNA at stalled replication forks is degraded in a manner similar to other repair mutants. [¹⁴C]-thymine-labeled cultures were pulse-labeled with [³H]-thymidine for 5 s before the cells were collected, resuspended in nonradioactive media, and UV-irradiated with 27 J/m². The fraction of ¹⁴C-labeled genomic DNA (□) and ³H-labeled nascent DNA (■) remaining over time is plotted. Graphs represent the average of three independent experiments. The level of [³H] and [¹⁴C] in DNA immediately preceding irradiation ranged between 2500–7000 cpm and 1000–2500 cpm in all experiments. Error bars represent the standard error of the mean.