Tubulin units are the building blocks of microtubules. When the microtubule is no longer needed, it can separate/break down into tubulin units.
If this question is part of your mitosis/meiosis homework, then the question is probably asking how the microtubules pull chromatids to the poles of the cell to separate them before cell division. The answer to that is, the length of the microtubule is shortened when tubulin units are removed, and the chromatid is pulled along as it shrinks in size.
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Break down? Separate?
Tubulin units are the building blocks of microtubules. When the microtubule is no longer needed, it can separate/break down into tubulin units.
If this question is part of your mitosis/meiosis homework, then the question is probably asking how the microtubules pull chromatids to the poles of the cell to separate them before cell division. The answer to that is, the length of the microtubule is shortened when tubulin units are removed, and the chromatid is pulled along as it shrinks in size.
Hope that was what you needed.