Before You Begin
Question #45351
The Question
During an in vitro fertilization (IVF) experiment, a human secondary oocyte is treated with a mild dose of colchicine immediately prior to the entry of a sperm. Assuming sperm penetration is successful, which of the following best describes the most likely immediate consequence on oogenesis and the resulting zygote?
Options
- A.
The secondary oocyte will fail to complete Anaphase II due to the inhibition of microtubule polymerization, resulting in the non-extrusion of the second polar body and a triploid zygote.
- B.
The secondary oocyte will remain permanently arrested in the Diplotene stage of Prophase I, as colchicine prevents the dissolution of the synaptonemal complex.
- C.
The sperm will fail to induce the completion of Meiosis II because colchicine directly denatures the Anaphase Promoting Complex (APC) required for chromatid separation.
- D.
The second polar body will be extruded normally, but the zygote will arrest at Metaphase of its first mitotic cleavage due to the destruction of the sperm-derived proximal centriole.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Meiosis_II|Secondary_Oocyte|Spindle_Fiber_Disruption
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students must integrate three distinct NCERT concepts: the specific stage of meiotic arrest in a mature ovum (Metaphase II), the trigger for its completion (sperm entry), and the cellular mechanism of colchicine (microtubule inhibition).
The common misconception is failing to realize that blocking the spindle apparatus during fertilization prevents the extrusion of the second polar body, directly leading to polyploidy/aneuploidy.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Reproduction - Class 12 |
| Concept | Meiotic Arrest Points |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |