Fig. 5. Weak attachment greatly reduces kinetochore microtubule accumulation. (A-C) Phase contrast images of the cell in life. Arrows in A, B and ‘w’ and ‘u’ in C, kinetochores of the manipulated chromosome; arrowheads, some control kinetochores. (A) Before the operation. (B) Both kinetochores (arrows in A and B) of one chromosome were detached from spindle microtubules and the chromosome was moved to the cytoplasm and kept from reattaching for 10 minutes. (C) One kinetochore (‘w’) was then allowed to attach to spindle microtubules but the other one was not (‘u’), so that the attached kinetochore was not under tension and was weakly attached. After 10 minutes the cell was fixed for anti-tubulin immunofluorescence. (D,E) Superimposed phase contrast and immunofluorescence images (D) and immunofluorescence alone (E). The kinetochore that was not under tension (‘w’ in D) had a very weakly fluorescent kinetochore microtubule bundle (arrow) compared with the bundles of the controls (arrowheads) that had been under tension. Bar, 10 µm.