Figure 5.

Analysis of S phase progression in cell cycle mutants. E1000 (wild-type), E742 (clb5Δclb6Δ) and E996 (cdc6-1) cultures were arrested in G₁ phase with α-factor and released by addition of pronase in medium containing 400 µg/ml BrdU. cdc6-1 cells were pre-synchronized in G₂/M with nocodazole and maintained at 37°C in order to inactivate Cdc6p prior to α-factor release. (A) Genomic DNA was extracted from agarose plugs identical to those used in (B) and the total amount of BrdU incorporated was quantitated as described in Materials and Methods. (B) Percentage of S phase completion estimated from re-entry of BrdU-labeled chromosomes into the PFGE gel. (C) Kinetics of DNA replication as seen by FACS analysis of DNA content in the three cultures.