Antimetabolites primarily act during which phase of the cell cycle?

Antimetabolites primarily act during which phase of the cell cycle?

• A. G1
• B. S
• C. M
• D. G2

Answer: (B)

Antimetabolites disrupt DNA synthesis by acting as nucleotide analogs or by blocking nucleotide production. DNA replication occurs in the S phase, so these drugs are most effective when the cell is actively synthesizing DNA. By depleting the nucleotide pool or getting incorporated into DNA, they stall replication and trigger cell death in cells undergoing S-phase replication. That makes this phase the one where antimetabolites exert their primary cytotoxic effect. In G1, cells aren’t duplicating their DNA yet, so interference with nucleotide synthesis has less immediate impact. In G2, the DNA has already been replicated, and in M, the cell is focused on mitosis rather than DNA synthesis, so antimetabolites are less targeted there.

Antimetabolites disrupt DNA synthesis by acting as nucleotide analogs or by blocking nucleotide production. DNA replication occurs in the S phase, so these drugs are most effective when the cell is actively synthesizing DNA. By depleting the nucleotide pool or getting incorporated into DNA, they stall replication and trigger cell death in cells undergoing S-phase replication. That makes this phase the one where antimetabolites exert their primary cytotoxic effect.

In G1, cells aren’t duplicating their DNA yet, so interference with nucleotide synthesis has less immediate impact. In G2, the DNA has already been replicated, and in M, the cell is focused on mitosis rather than DNA synthesis, so antimetabolites are less targeted there.