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Question #45115
The Question
A transgenic sheep is developed via microinjection to express a human therapeutic protein in its blood. While Northern blotting confirms high expression of the transgene mRNA, a sandwich ELISA designed to quantify the human protein in the sheep's serum yields a near-zero signal after a few weeks. Which of the following best explains this diagnostic discrepancy?
Options
- A.
The sheep's humoral immune system produced endogenous antibodies against the heterologous protein, masking its epitopes and preventing ELISA capture antibodies from binding.
- B.
The heterologous protein lacked a secretory signal peptide, causing it to be rapidly degraded by serum lysozymes before detection.
- C.
The primary immune response generated cytotoxic T-cells that directly phagocytosed the circulating recombinant protein.
- D.
The microinjected gene underwent alternative splicing, producing a protein variant that competitively inhibited the ELISA enzyme substrate.
Check Your Answer
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
Microinjection Specificity|ELISA Logic|Antibody Structure Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Integrating Biotechnology (Ch 12) with Immunology (Ch 8).
Students often treat transgenic animals as inert 'bioreactors' and forget they possess active immune systems.
The trap tests the understanding of competitive inhibition in serological assays—specifically, how endogenous host antibodies can cause steric hindrance and epitope masking, leading to false-negative ELISA results despite successful gene expression.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Microinjection Specificity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |