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Question #45376
The Question
In a geographically isolated mammalian population, a mutation alters the spatial topology of the ZP3 glycoprotein on the zona pellucida of the ova. If females from this mutated population are mated with wild-type males of the original species, which of the following represents the most accurate physiological and evolutionary outcome?
Options
- A.
Unrestricted entry of multiple sperms due to the failure of the zona reaction, leading to lethal polyspermy.
- B.
Failure of the acrosome reaction in wild-type sperms, establishing gametic isolation as a pre-zygotic barrier.
- C.
Immediate induction of the cortical reaction prior to sperm contact, causing post-zygotic reproductive isolation.
- D.
Successful penetration of the zona pellucida but failure of syngamy due to structural incompatibility of the pronuclei.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
ZP3_Glycoprotein|Sperm_Bindin|Species_Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between initial sperm-zona binding (gamete recognition via ZP3) and the subsequent zona reaction (polyspermy block via cortical granules).
The common misconception is assuming any defect in the zona pellucida automatically leads to polyspermy.
Students must realize that without the primary ZP3 receptor, fertilization cannot even initiate, effectively acting as an evolutionary pre-zygotic barrier.
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 |