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Question #45359
The Question
A genetic mutation in E. coli leads to the constitutive expression of the lac operon. Concurrently, a clinical case reveals a mammalian endocrine disorder where a peptide hormone's half-life is drastically reduced, causing continuous glandular hypersecretion but target tissue desensitization. Which of the following accurately contrasts the underlying regulatory mechanisms of these two systemic failures?
Options
- A.
The bacterial system fails at the transcriptional gate due to operator-repressor dissociation, whereas the mammalian system fails at the signal transduction threshold due to altered ligand-receptor kinetics and diminished negative feedback.
- B.
Both systems exhibit a failure in negative regulation because the inducer in bacteria and the hormone in mammals permanently bind to their respective regulatory genes to maintain continuous expression.
- C.
The lac operon becomes constitutive due to the continuous presence of a corepressor, while the endocrine disorder results from the up-regulation of intracellular receptors in response to the shortened hormone half-life.
- D.
The bacterial failure is an example of disrupted positive regulation by the i gene, whereas the mammalian failure demonstrates positive feedback loop amplification due to rapid hormone degradation.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Allolactose|Repressor_Protein|Operator|Hormone_Receptors
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between transcriptional gating (bacterial operons) and signal transduction/feedback loops (mammalian endocrinology).
Students often confuse the mechanism of 'constitutive' or 'continuous' activity, assuming both involve direct gene activation by the ligand.
The trap lies in recognizing that bacterial negative feedback involves physical repressor-operator binding, while endocrine negative feedback relies on systemic circulating levels (half-life) and receptor sensitivity (down-regulation).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Reproduction - Class 12 |
| Concept | Hormonal Feedback Loops |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |