In animal cells, a certain anticancer drug disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. This stops mitosis from proceeding. What specific process must this anticancer drug affect?

a. Chromatid assembly
b. Formation of the mitotic spindle
c. Formation of the centrioles
d. The S phase of the cell cycle

b. Formation of the mitotic spindle

Explanation:

The mitotic spindle is made of microtubules. Microtubules are the polymers of tubulin proteins. The formation of the spindle starts in prophase. It is required to align the chromosomes at the cell's equator during metaphase. This is followed by splitting of centromere and separation of two sister chromatids to the opposite poles of the cell. The shortening of microtubules of the spindle during anaphase assist in the chromosome movement. Therefore, the mitotic spindle is required for cell division to occur. Anticancer drugs do not allow the formation of the spindle by interfering in the assembly of tubulin protein subunits.