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Question #45348
The Question
Consider the chronological and genetic events of human gametogenesis and seed development in Citrus. Which of the following statements is INCORRECT regarding their respective mechanisms of embryo or zygote formation?
Options
- A.
In human oogenesis, the completion of meiosis II is strictly contingent upon sperm entry, whereas Citrus nucellar embryos develop without any requirement for syngamy.
- B.
Unlike human spermatogenesis which involves continuous meiotic divisions from puberty, the formation of adventive embryos in Citrus completely bypasses reductive division.
- C.
While a human zygote is formed by the fusion of haploid gametes, the multiple embryos in a Citrus seed typically arise from the unfertilized haploid cells of the embryo sac, such as synergids.
- D.
Human oogenesis exhibits chronological arrest at Prophase-I and Metaphase-II, whereas Citrus polyembryony yields diploid embryos that are exact genetic clones of the maternal sporophyte.
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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
Spermatogenesis vs. Oogenesis Chronology|Polyembryony Mechanisms
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Location Trap: Students often confuse the specific mechanisms of apomixis.
Because the final embryos are located inside the embryo sac, a common misconception is that they must originate from the haploid cells within it (e.g., synergids undergoing parthenogenesis).
The trap relies on the student forgetting that Citrus polyembryony is specifically 'sporophytic budding' from the diploid nucellus located outside the embryo sac initially.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Reproduction - Class 12 |
| Concept | Spermatogenesis vs. Oogenesis Chronology |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |