Metaphase PtK1 cell microinjected with X-rhodamine-labeled tubulin and Alexa 488-labeled CENP-F antibodies, to fluorescently label kinetochore fibers (red) and kinetochores/spindle poles (green), respectively.

The movie shows that sister kinetochore pairs oscillate between the two spindle. The top kinetochore of the first sister pair on the right exhibits abnormal attachment to spindle microtubules, as it is bound to microtubules coming from both spindle poles, rather than just one (merotelic kinetochore orientation). As a consequence of this mis-attachment, the merotelically oriented kinetochore remains relatively stationary while its normally oriented sister oscillates between poleward and anti-poleward movements.

Digital images were acquired every 20-60 seconds at a 60X magnification. Elapsed time is shown in min:sec