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Question #45375
The Question
During an in vitro fertilization experiment, a mammalian ovum is treated with a specific neurotoxin analogue that selectively blocks voltage-gated Na+ channels on the oolemma. Upon exposure to capacitated sperms, which of the following represents the most likely immediate physiological consequence and the ultimate genetic fate of the resulting zygote?
Options
- A.
The fast block to polyspermy fails, resulting in multiple sperm entry and the formation of a polyploid, non-viable embryo.
- B.
The slow block to polyspermy is inhibited due to the lack of membrane depolarization, leading to an aneuploid zygote.
- C.
Cortical granules undergo premature exocytosis, causing the zona pellucida to harden before any sperm can penetrate.
- D.
The ovum fails to complete Meiosis II due to the absence of a sodium influx, resulting in the retention of the second polar body.
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
Fast_Block_to_Polyspermy|Resting_Membrane_Potential|Sodium_Influx
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing the ionic basis of the fast block (Na+ influx/depolarization) from the slow block (Ca2+ release/cortical reaction), and differentiating the genetic consequences of polyspermy (Polyploidy vs Aneuploidy).
Students often confuse the roles of Na+ and Ca2+ in fertilization and incorrectly use 'aneuploidy' interchangeably with 'polyploidy'.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Reproduction - Class 12 |
| Concept | Polyspermy Prevention Mechanisms |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |