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Question #45479
The Question
An exogenous gene is microinjected into a diploid Microspore Mother Cell (MMC) just before it enters meiosis. During the pachytene stage of Prophase I, a targeted chemical transiently inhibits the 5' → 3' phosphodiester bond formation activity of DNA ligase. Which of the following is the most likely outcome regarding the transgene, and why?
Options
- A.
The transgene may fail to stably integrate into the recombining chromatids, producing a mosaic microspore tetrad that complicates the recovery of homozygous transgenic lines.
- B.
The transgene will be uniformly distributed to all four microspores because the sealing of DNA nicks during crossing over is exclusively mediated by the enzyme recombinase.
- C.
The MMC will fail to complete the pre-meiotic S phase, resulting in the complete degradation of the transgene before the ploidy shift occurs.
- D.
The transgene will be successfully integrated, but its segregation will be restricted to the vegetative cell due to the lack of ligase activity during post-meiotic mitosis.
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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
Taq_Polymerase_Thermal_Stability|Microinjection_Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often restrict the role of DNA ligase to DNA replication (joining Okazaki fragments) and rDNA technology (joining vectors), failing to recognize its critical role in sealing DNA nicks during meiotic crossing over (recombination nodules).
The trap also tests the temporal sequence of meiosis, ensuring students know that S-phase precedes the pachytene stage.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Microsporogenesis Ploidy Shift |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |