In the context of oncogenes and tumor suppressors, how would loss of p53 activity most directly affect a cell?

• A. The cell would fail to initiate DNA replication because p53 is the essential helicase required to unwind replication origins.
• B. The cell would be less able to arrest the cell cycle or trigger apoptosis in response to DNA damage, increasing survival of genetically unstable cells.
• C. The cell would be unable to activate telomerase, leading to immediate senescence in all dividing cells.
• D. The cell would have constitutively active Ras signaling because p53 normally functions as a Ras GTPase-activating protein (GAP).

Answer: (B)