Selected MCQ

Current Question
Which cell cycle checkpoint is specifically responsible for preventing the onset of anaphase until all chromosomes are properly attached to the spindle apparatus?
  • A. G1/S checkpoint
  • B. G2/M checkpoint
  • C. Spindle assembly (metaphase) checkpoint
  • D. DNA damage checkpoint
Correct Answer: C
Explanation:
The spindle assembly (metaphase) checkpoint delays anaphase until every chromosome is correctly attached to the mitotic spindle, ensuring accurate chromosome segregation.
Related Question 1
During the eukaryotic cell cycle, which checkpoint ensures that all chromosomes are correctly attached to the mitotic spindle before proceeding to anaphase?
  • A. G1/S checkpoint
  • B. G2/M checkpoint
  • C. Spindle (metaphase) checkpoint
  • D. S-phase checkpoint
Correct Answer: C
Explanation:
The spindle assembly (metaphase) checkpoint monitors attachment of all kinetochores to spindle microtubules. It prevents the onset of anaphase until all chromosomes are properly aligned and attached.
Related Question 2
Why is the G0 phase considered distinct from G1 in the cell cycle?
  • A. G0 cells are rapidly dividing
  • B. G0 is a quiescent/nondividing state outside the normal cycle
  • C. G0 occurs immediately after the M phase in all cells
  • D. Cells in G0 cannot re-enter the cell cycle under any condition
Correct Answer: B
Explanation:
G0 is a resting or terminal differentiation state where cells are metabolically active but not dividing. Cells can re-enter G1 from G0 given appropriate signals.
Related Question 3
Which cell cycle regulator acts as a tumor suppressor that can halt cell cycle progression after DNA damage?
  • A. Cyclin D
  • B. p53
  • C. E2F
  • D. Myc
Correct Answer: B
Explanation:
p53 induces cell cycle arrest or apoptosis in response to DNA damage, preventing propagation of mutations, and is a classic tumor suppressor.
Related Question 4
Which organelle is primarily responsible for lipid synthesis and detoxification of drugs in liver cells?
  • A. Rough endoplasmic reticulum
  • B. Smooth endoplasmic reticulum
  • C. Golgi apparatus
  • D. Mitochondrion
Correct Answer: B
Explanation:
Smooth ER contains enzymes involved in lipid metabolism and drug detoxification (e.g., cytochrome P450s), especially in hepatocytes.
Related Question 5
The checkpoint that verifies DNA is completely replicated and undamaged before a cell enters mitosis is called:
  • A. G1/S checkpoint
  • B. S-phase checkpoint
  • C. G2/M checkpoint
  • D. Spindle assembly checkpoint
Correct Answer: C
Explanation:
The G2/M checkpoint ensures that all DNA has been accurately replicated and that any damage is repaired before mitosis. If errors are found, the cycle is halted for repair.