A defect in centromeric cohesion affects Kt biorientation. (A and B, top) Image series showing an ndc80-gfp cdc11-cfp cell (A) or a rad21-K1 ndc80-gfp cdc11-cfp cell (B) during mitosis. The six Kts (green) are located between the two SPBs (red). Schematic representations of fission yeast cell shape are shown (dashed ovals). (middle) Kymograph of the cell shown above. In control cells, anaphase A (arrows) takes place ∼45 s before anaphase B (asterisk). The number of Kts at each SPB is indicated for each time point on both sides of the kymograph. (bottom) Automated tracking analysis of SPB (red) and Kt (green) positions in the same cell (see Materials and methods). (C) Percentage of mitotic cells with stretched merotelic Kts in rad21-K1 ndc80-gfp cdc11-cfp cells (rad21-K1). (D) Percentage of cut-like phenotype and asymmetric cells in wt (n = 2,466) and rad21-K1 cells (n = 1,966) stained with DAPI calcofluor. White, correct segregation with a septum; gray, cut cells; black, asymmetrically dividing cells. Error bars indicate SD.