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Question #45113
The Question
A researcher uses a disarmed Ti plasmid of Agrobacterium tumefaciens to introduce a mammalian gene into a tobacco plant. Southern blot analysis confirms stable T-DNA integration, and Northern blot detects abundant primary transcripts (hnRNA). However, the transgenic plant produces only truncated, non-functional polypeptides. Which of the following is the most scientifically accurate explanation for this phenomenon?
Options
- A.
The plant's spliceosome machinery failed to accurately recognize the mammalian splice donor and acceptor sites, leading to aberrant mRNA processing.
- B.
The T-DNA integrated into a transcriptionally inactive heterochromatin region of the plant genome, causing gene silencing.
- C.
The vir region of the Ti plasmid was deleted during the disarming process, preventing necessary post-transcriptional modifications.
- D.
The mammalian gene lacked a Shine-Dalgarno sequence, which is strictly required for translation initiation by plant 80S ribosomes.
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
T-DNA|Intron_Processing|Spliceosome|Post-transcriptional_Modification
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that successful T-DNA integration and transcription automatically guarantee functional protein expression.
The trap lies in ignoring host-specific post-transcriptional processing (splicing).
The question also tests data interpretation: the presence of hnRNA on a Northern blot must be used to eliminate transcriptional silencing as a distractor.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Agrobacterium Tumefaciens Mechanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |