Answer: Spindle assembly checkpoint failure causing chromosome mis-segregation.
- A Failure of enzymatic DNA repair machinery to fix existing damage
- B Spindle assembly checkpoint failure causing chromosome mis-segregation
- C Excessive, uncontrolled rounds of DNA replication occurring repeatedly
- D Endoreduplication occurring alone without any subsequent cell division
Correct answer: B. Spindle assembly checkpoint failure causing chromosome mis-segregation
Explanation: Aneuploidy (abnormal chromosome number) most commonly arises from SAC failure or cohesion defects causing unequal chromosome segregation during mitosis or meiosis.
The cell cycle: G1 (growth and preparation), S (DNA replication, chromosome number stays 2n but DNA content doubles), G2 (final checks before division), and M (mitosis itself) - together, G1+S+G2 make up interphase.
Concept context
Mitosis and meiosis: how cells divide for growth, repair, and reproduction.