Spindle elongation in ctf4 mutant cells exposed to HU. A and B. Cells of 699 (CTF4) and 699Dctf4 (ctf4) were arrested in G1 phase at 30°C in YEPD medium using α-factor and then released in the same medium at the same temperature in the presence of 0.2 M HU for 3 hours. Thereafter, the cells were processed for spindle staining using anti-α-tubulin antibody. The figure shows wild-type and ctf4 cells having, respectively, short and elongated mitotic spindles. The graphical representation of the distribution of spindle lengths (around 250 for each) is shown in the right panel.