Long chromosomes correct errors less efficiently. (A) Real-time error correction scheme: STLC washout allows monopolar spindles, enriched in attachment errors, to recover bipolarity and perform error correction. (B) Representative time lapse of error correction assay in PtK2 cells expressing eYFP-Cdc20 and mCherry-α-tubulin. Arrowheads denote long chromosomes stuck in erroneous attachments. One short chromosome is highlighted in pink and three incorrectly attached long chromosomes are highlighted in blue. See also Video 3. (C) Raw alignment time of short chromosomes (<7 µm) and long chromosomes (≥7 µm) in cell shown in B. (D) Normalized alignment time for population such that time t = 0 is the time of the first chromosome oscillating at the metaphase plate following drug washout and t = 1 is the time the last chromosome begins oscillating prior to anaphase (mean ± SD; Mann–Whitney test). (E) Mean kinetochore speed of long and short chromosomes with respect to the pole in monopolar spindles (mean ± SD; unpaired t test).