Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Cancer cells display a high level of heterogeneity in the expression of TP53 protein.
Which of the following techniques can be directly used to determine the intra -
tumoral heterogeneity of TP53 expression in a given tumor sample , without
resorting to additional cell separation techniques?
Options:
(A) Immunoblotting
(B) Flow cytometry
(C) ELISA
(D) Quantitative RT-PCR
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.14)**
**1. Governing Concept**:
- **Topic**: Analytical Biotechnology & Flow Cytometry / Single-Cell Proteomics
- To analyze heterogeneous protein expression (such as p53) in individual cancer cells within a heterogeneous population:
- Bulk assays (Western blot, ELISA) measure average population expression, masking cell-to-cell variability.
- **Intracellular Flow Cytometry (FACS)** or single-cell mass cytometry (CyTOF) measures fluorescence intensity per individual cell across tens of thousands of cells, directly quantifying single-cell expression distributions and identifying sub-populations.
**2. Option Analysis**:
- **Option (A) [Western Blotting] is INCORRECT**: Provides an aggregate average band signal from bulk cell lysates without single-cell resolution.
- **Option (B) [Flow cytometry] is CORRECT**: Permits quantitative measurement of fluorescence-labeled intracellular TP53 on a cell-by-cell basis, resolving heterogeneity.
- **Option (C) [ELISA] is INCORRECT**: A bulk ensemble plate-based assay.
- **Option (D) [Northern Blotting] is INCORRECT**: Measures bulk mRNA levels, not protein heterogeneity.
**3. Final Answer**:
- **Correct Choice**: **B**
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