Dynamics of the poleward transport response suggest it acts rapidly and moves chromosomes robustly across different spindle architectures. (A) Change in the distance from chromosomes to the pole before and after ablation of their k-fibers in metaphase bipolar spindles. After ablation, chromosomes attached to ablated k-fibers (blue traces, n = 18) are pulled poleward, whereas neighboring control chromosomes (green traces, n = 14) continue oscillating. (B) Change in the distance from chromatids to the pole before and after ablation of their k-fibers during anaphase. Chromatids attached to ablated k-fibers (blue traces, n = 10) are pulled toward poles faster than anaphase movement of their unmanipulated sister chromatids (green traces, n = 10) before resuming normal anaphase movement around 70 s. See also Fig. S2. (C) Change in the distance from chromosomes to the pole before and after the ablation of their k-fibers in monopolar spindles. After ablation of their k-fibers, chromosomes are rapidly pulled toward poles (blue traces, n = 37) before resuming normal oscillations. (D) Zoom of traces from C displaying only from start to end of the poleward transport response of each trace, synchronized to individual response start times (0 s). (E) Change in the distance from chromosomes to the pole during repeated ablation experiments in bipolar (top) and monopolar (bottom) spindles (four example traces of each). Traces are shown in gray before the first ablation, in solid blue after the first ablation (which severs the k-fiber), and in solid red after the second ablation (which destroys the new, free minus ends). Dotted lines connect points before and after ablation. Poleward transport begins after the first ablation but temporarily stops when the k-fiber stub minus end is destroyed by the second ablation, suggesting that poleward transport requires mechanical engagement of the minus end.