B. TEM analysis of SPBs. PHSL1-CDC20 ama1∆ cells containing SPC72 or spc72-7 were shifted from 24 to 36°C at 4 h in SPM. TEM samples were collected at 12 h in SPM. Spc72 inactivation causes MP formation at metaphase I (P < 0.0001, Fisher's exact test). Scale bar, 0.2 μm. 