Figure 9.

Dna2p executes its function at around the time of late S phase. (A and B) dna2–22 cells lose viability at 37°C but not 30°C. (A) Strains YDF100 (DNA2⁺) and YDF102 (dna2–22) were synchronized with α factor and released at 30°C. In panel B, YDF102 (dna2–22) cells were synchronized as in panel A but then preincubated at 37°C for various times before α factor release. Aliquots were taken at the times shown and assayed for colony-forming ability at 30°C. All numbers are normalized to values at t = 0 after α factor release. The black bar in panel B represents the time of DNA synthesis (see panel C) in the 1-h preincubation samples. (C) Kinetics of DNA synthesis in the dna2–22 mutant. Aliquots of cells from the 1-h preincubation protocol in panel B were taken every 10 min after α factor release and analyzed for DNA content by FACS analysis.