p53's Role in Preventing DNA Replication Errors

Steps:

• p53 protein detects damaged DNA in interphase and halts replication to allow repair.
• Mutation from carcinogen inactivates p53, removing the checkpoint.
• Damaged DNA then replicates, leading to mutations in daughter cells.
• Accumulated mutations disrupt cell cycle control, promoting cancer.

Why B is correct:

• p53 acts as a tumor suppressor by enforcing the G1/S checkpoint (definition from cell biology), so its absence allows replication of damaged DNA, accumulating oncogenic mutations.

Why the others are wrong:

• A: Mitosis occurs after S phase; p53 primarily blocks DNA replication, not directly mitosis.
• C: Mutated p53 does not cause division; intact p53 prevents it.
• D: p53 inhibits, rather than causes, uncontrolled division.

Final answer: B