Answer :
Microtubules can grow by addition of tubulin dimers to the plus end, and they can shorten by removal of dimers from the minus end, hence the correct option is a) the plus end; the minus end.
Microtubules are dynamic structures composed of tubulin protein subunits. Their growth occurs primarily by the addition of tubulin dimers to the plus end, which is the end where polymerization occurs more rapidly. Conversely, microtubules shorten by the removal of tubulin dimers from the minus end, which is the end where depolymerization takes place.
This dynamic instability allows microtubules to rapidly reorganize and participate in various cellular processes such as cell division, intracellular transport, and cell shape maintenance. Options B, C, and D are incorrect because they do not accurately describe the directional growth and shortening of microtubules.
