chl1 cells show increased spindle lengths in the presence of HU and MMS. A. DNA and mitotic spindles of mutant and wild-type cells treated with HU. Exponentially growing cells AP22 (CHL1) and AP22Dchl1 (chl1) were treated with 0.2 M HU for 2.5 hours and cells were processed for nuclei and spindle staining. B. Spindle extension occurs in S-phase. 699 (CHL1) and 699Dchl1 (chl1) cells were arrested by alpha-factor at G1 and released in fresh YEPD containing 0.2 M HU. Aliquots were removed at various time points in S-phase for tubulin staining and flow cytometry. Mitotic spindles of wild-type and mutant cells treated with HU for 2.5 hours are shown. Graphical representation of the distribution of spindle lengths at the corresponding time point is also shown. C. DNA content of cells in Figure 2B measured by flow cytometry. D. Graphical representation of the percentage of cells having spindles greater than 2 μm in wild-type and chl1 cell cultures at indicated time points of HU treatment. E. 699 (wild-type) and 699Dchl1 (chl1) cells were arrested by alpha-factor in G1 and released in fresh YEPD containing 0.035% MMS. Aliquots were removed for spindle staining of cells treated with MMS for 1.5 and 2 hours. F. DNA content of cells in Figure 2E measured by flow cytometry. Arrows indicate G1 and G2 DNA contents. 'h' refers to hours.