Movement of the chromosomes during anaphase would be most affected by a drug that prevents

Movement of the chromosomes during anaphase would be most affected by a drug that prevents shortening of microtubules.

Explanation:

The anaphase stage of mitosis - anaphase A and anaphase B stages - results in the separation of the sister chromatids and the movement of the daughter chromatids to the cellular poles.

This chromosomal separation takes place by the depolymerisation and shortening of the microtubules (kinetochore, interpolar, and astral) in the mitotic spindles and by the force generated by them.

These microtubules are formed of tubulin protein monomers which assemble and disassemble during a normal mitotic cell division.

Mitotic inhibiting drugs like plant alkaloids, taxols interfere with this microtubular shortening action and thereby interferes mitotic cell division.