During what phases in the cell cycle would you expect there to be large changes in the polymerization or depolymerization of microtubules? why are these changes necessary?

The polymerization or depolymerization of microtubules usually takes place on the M-phase of the cell cycle. Also known as the mitotic phase, it is a process in the cell cycle wherein the mother cell would be divided into two identical daughter cells using mitosis and cytokinesis.