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Question #45499
The Question
In a transgenic angiosperm, RNA interference (RNAi) is utilized to specifically silence the expression of genes encoding the secretory attractant proteins of the synergids. Which of the following best describes the cytological state and reproductive outcome of the mature ovule?
Options
- A.
A structurally normal 7-celled, 8-nucleate embryo sac is formed, but double fertilization is prevented due to the loss of pollen tube guidance.
- B.
The embryo sac arrests at the 4-nucleate stage because synergid-derived transcripts are essential for the final mitotic divisions of megagametogenesis.
- C.
The pollen tube successfully enters the synergid but fails to discharge the male gametes due to the physical degradation of the filiform apparatus.
- D.
The pollen tube bypasses the synergids and enters the central cell directly, resulting in primary endosperm nucleus (PEN) formation without syngamy.
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
Embryo Sac Nuclei Count|RNA Interference (RNAi) Mechanism|Filiform Apparatus
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the structural development of the embryo sac (megagametogenesis) and its functional biochemical interactions (chemotaxis).
A common misconception is that silencing a gene in a specific cell type will arrest the entire developmental pathway of the tissue.
Here, students must deduce that RNAi specifically targets the post-developmental function (secretion of attractants) rather than the mitotic divisions, leaving the embryo sac structurally mature but functionally isolated.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Embryo Sac Nuclei Count |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |