Fig. 3.

The different routes to kinetochore biorientation. a Direct simultaneous end-on attachment of sister kinetochores with microtubules from both poles. b The mono-oriented sister chromosomes are pushed in an anti-poleward manner by PEF to increase the probability that the opposing sister kinetochore can make a direct end-on attachment with a microtubule from the opposite pole. c The chromosomal Ran-GTP gradient assists microtubule nucleation from the kinetochore, which may then bind directly to microtubules from the distal pole. d The mono-oriented chromosome is transported towards the distal pole along an existing kinetochore fiber by the plus-end directed motor, CENP-E, which binds to the unattached sister kinetochore. This increases the chance of encountering a microtubule emanating from the distal pole