Cell cycle and apoptosis · USMLE Step 1

Which checkpoint prevents a cell with DNA damage from entering S phase, allowing time for repair or triggering cell death if damage is irreparable?

  1. G2/M checkpoint
  2. Spindle (M) checkpoint
  3. G1/S checkpoint
  4. Cytokinesis checkpoint
Show answer and explanation

Correct answer: G1/S checkpoint

The G1/S checkpoint (or restriction point) assesses cell size, DNA integrity, and external signals; if DNA damage is detected, the cell can arrest or activate repair mechanisms, preventing entry into S phase.

Difficulty: Medium Question 3 of 19

Practice all 19 Cell cycle and apoptosis questions

Keep practicing

More Cell cycle and apoptosis questions