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Question #45886
The Question
A research scientist isolates the complete genomic DNA sequence of the human insulin gene and successfully clones it downstream of a strong bacterial promoter in an E. coli expression vector. Despite successful transcription and translation, the resulting polypeptide is entirely non-functional and significantly larger than human proinsulin. Which of the following best explains this systemic failure?
Options
- A.
E. coli lacks the Golgi apparatus required for the formation of disulfide bridges between the A and B chains.
- B.
The prokaryotic host lacks the snRNP-dependent spliceosomal machinery, resulting in the translation of intronic sequences.
- C.
The bacterial RNA polymerase fails to recognize the eukaryotic terminator, causing read-through transcription.
- D.
E. coli lacks the specific endopeptidases needed to cleave the C-peptide from the synthesized proinsulin.
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
Exons|Introns|Proinsulin_to_Insulin
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the inability of bacteria to process proinsulin (post-translational cleavage of the C-peptide) with their inability to process hnRNA (post-transcriptional splicing of introns).
The trap (Option D) tests if the student notices the phrase 'significantly larger than human proinsulin', which dictates that the failure occurred at the RNA splicing level, necessitating the use of synthetic DNA or cDNA (as done by Eli Lilly in 1983).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Transcriptional Unit Boundaries |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |