How do many chemotherapy drugs affect the cell cycle?

Many chemotherapy drugs impact the cell cycle primarily by arresting the cell in the M phase, which is the phase associated with mitosis. During this critical point in the cell cycle, the cell is actively dividing and separating its chromosomes into two daughter cells. Chemotherapy agents often target rapidly dividing cells—such as cancer cells—by interfering with processes that occur during this phase, thereby preventing the completion of mitosis. This disruption can lead to cell death or a significant reduction in the proliferation of cancer cells, as they are unable to progress through and complete cell division.

In contrast, other choices involve mechanisms that would not effectively prevent cancer cell growth or division. Promoting rapid cell division would be counterproductive since the goal of chemotherapy is to halt the uncontrolled growth of cancer cells. Inhibiting glucose metabolism and enhancing DNA replication would not directly lead to cell cycle arrest; rather, they concern cellular metabolism and DNA synthesis, respectively, which are not the primary targets of many chemotherapy drugs in their action against the cell cycle. Thus, the correct answer is rooted in the direct mechanism by which these medications disrupt mitotic processes crucial for cell division.