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Question #46417
The Question
Evolutionary biologists often utilize the constant accumulation rate of neutral mutations in non-coding DNA as a 'molecular clock' to estimate the geological time of divergence between species. Suppose a mutation deletes the terminator region of a transcription unit, causing RNA polymerase to continuously read through into an adjacent, previously non-transcribed DNA region. Which of the following statements correctly describes the consequence of this event on evolutionary studies?
Options
- A.
The region becomes a more reliable molecular clock because continuous RNA polymerase activity prevents DNA repair enzymes from fixing neutral mutations.
- B.
The molecular clock calibration against geological time fails because the previously neutral region is now transcribed, subjecting it to selective pressure and altering its mutation rate.
- C.
The mutation rate will strictly double and align with stellar evolutionary time scales due to the uncoupling of the transcription block.
- D.
There is no effect on the molecular clock because transcription utilizes the template (non-coding) strand, whereas molecular clocks exclusively rely on the 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
Stellar Distance vs. Geological Time|Non-Coding Strand Utility|Transcriptional Unit Boundaries
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'non-coding DNA = molecular clock' without understanding that its utility depends entirely on the absence of selective pressure.
The question tests the synthesis of Molecular Genetics (transcription unit boundaries) and Evolution (molecular clocks).
The primary trap (Option D) exploits the overlapping nomenclature between the 'non-coding (template) strand' of a gene and 'non-coding DNA' (intergenic regions), testing if the student truly understands the physical reality of the DNA double helix and transcription.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Stellar Distance vs. Geological Time |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |