Figure 3.

Increased degradation occurs at the growing fork after irradiation in recF and recR cells. [³H]Thymine was added to [¹⁴C]thymine-prelabeled cells for 30 sec immediately before the cells were filtered and irradiated with 25 J/m² in nonlabeled medium. The fraction of the radioactive nucleotides remaining in the DNA is plotted over time. (▪, □) Parental cells, (•, ○) recF, (▴, ▵) recR. Loss of ¹⁴C genomic DNA (open symbols) can be compared with the loss of the [³H] DNA synthesized at the growing fork just before irradiation (filled symbols).