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Question #45888
The Question
A researcher induces a point mutation in a DNA sequence located towards the 5' end of the coding strand of an essential housekeeping gene in E. coli. This mutation results in a lethal phenotype characterized by the complete absence of the gene's mRNA transcript. Which of the following statements most accurately describes the primary molecular failure?
Options
- A.
RNA polymerase fails to recognize the promoter sequence, preventing transcription initiation on the 3' -> 5' template strand.
- B.
The mutation alters the start codon on the non-coding strand, completely inhibiting the initiation of translation by the ribosome.
- C.
The mutation disrupts the terminator sequence, preventing the release of the nascent mRNA and causing a lethal transcriptional read-through.
- D.
Sigma factor permanently binds to the mutated sequence, blocking the core enzyme from elongating the transcript along the 5' -> 3' coding strand.
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
RNA Polymerase|Template Strand|Promoter Sequence
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the reference polarity of the transcription unit.
NCERT explicitly states the promoter is at the 5' end of the coding strand, but transcription actually utilizes the 3' -> 5' template (non-coding) strand.
The trap tests both the anatomical location of the promoter and the functional distinction between the coding and template strands during RNA polymerase activity.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Non-Coding Strand Utility |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |