Fig. 2. Cdc45p is required for progression through S-phase. (A) Cycling cultures of cdc45-td and parental wild-type strains were arrested in G₁ with α factor at 24°C in YP plus raffinose. They were shifted to 37°C in YP plus galactose and held in α factor for 45 min. Cells were then released from the block at 37°C and samples were collected at the time points indicated and analysed by flow cytometry. (B) Budding index and percentage of cells with divided chromatin corresponding to the experiment shown in (A). (C) Logarithmic cultures of cdc45-td mutant and parental wild-type cells were arrested in G₁ with α factor at 24°C in YP plus raffinose. They were released from the arrest at 24°C in YP plus galactose, and after 60 min the cultures were shifted to 37°C. Samples were taken for flow cytometry analysis.