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Question #47754
The Question
A patient suffering from ADA deficiency (due to a homozygous gene deletion) undergoes somatic cell gene therapy. Functional ADA cDNA is introduced into their cultured lymphocytes via a retroviral vector, and the cells are infused back into the patient. Later, to monitor the persistence of the therapeutic gene, DNA is extracted from the patient's circulating lymphocytes and subjected to PCR. Despite the patient showing significant clinical improvement and normal ADA enzyme levels, the PCR yields a false-negative result (no amplification). Which of the following primer design errors most likely caused this?
Options
- A.
The primers were designed to span an intron-exon junction of the wild-type genomic ADA gene.
- B.
The primers were designed to be perfectly complementary to a sequence entirely within Exon 3 of the ADA gene.
- C.
The primers were designed to target the specific retroviral long terminal repeat (LTR) sequences flanking the cDNA.
- D.
The primers were designed to amplify the ADA gene, but the retroviral vector had integrated the gene into the patient's germline cells instead.
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
Heat Shock Thermal Gradient|Thermal Tolerance Ranges|Competent Cell Preparation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the structure of genomic DNA (contains introns and exons) and cDNA (contains only exons) used in gene therapy.
The trap relies on the student recognizing that a primer designed for native genomic architecture will fail to anneal to an engineered cDNA transcript, creating a false negative in clinical diagnostics.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Heat Shock Thermal Gradient |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |