Selected MCQ

Current Question
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.
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
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 3
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 4
Somatic cell nuclear transfer (SCNT) for reproductive cloning involves:
  • A. Injecting somatic cell DNA into a fertilized egg with its nucleus intact
  • B. Fusing a diploid somatic cell with an enucleated egg cell
  • C. Using only oocyte mitochondria from a donor
  • D. Cloning via binary fission
Correct Answer: B
Explanation:
SCNT (as in cloning Dolly the sheep) entails transferring the nucleus of an adult somatic cell into an enucleated oocyte, and then stimulating the resulting cell to divide as an embryo.
Related Question 5
In flow cytometry, cells are labeled with fluorescent antibodies and passed in a stream through a laser. This technique primarily measures:
  • A. Cell size and internal complexity
  • B. DNA sequence variants
  • C. Protein structure by X-ray diffraction
  • D. Glycolytic activity
Correct Answer: A
Explanation:
Flow cytometry measures light scattering (size and granularity) and fluorescence from labeled markers, allowing rapid analysis of cell populations (size, complexity, marker expression).