Figure 2.

  Chromosome bi‐orientation during prometaphase. When the nuclear envelope breaks down, the kinetochore is captured by lateral surfaces of microtubules emanating from a spindle pole (a), resulting in its transport towards that pole (arrow). High density of microtubules near the pole contributes to maturation of the lateral attachment to end‐on attachment, with the kinetochore tethered at the plus end of the microtubules (b). Polar ejection forces and/or gliding alongside microtubules attached to other already bi‐orientated chromosomes (not depicted in the figure) drive the mono‐orientated chromosome towards the metaphase plate (c), leading to its bi‐orientation (d). Attachment errors depicted in Fig. 3 can happen and are detected and corrected to bi‐oriented attachments.