Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Which one of the following techniques is used to monitor RNA transcripts, both temporally
and spatially?
Options:
(A) Northern blotting
(B) In situ hybridization
(C) Southern blotting
(D) Western blotting
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2018 Q.27)**
**1. Governing Concept & Question Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Topic**: Molecular Biology Techniques (Gene Expression Analysis & Spatial Transcriptomics)
**2. Detailed Step-by-Step Analysis**:
- The question asks for a technique to monitor RNA transcripts both **temporally** (at different developmental stages or time points) and **spatially** (within specific cells, tissues, or histological anatomical structures in intact tissue sections).
- **In situ hybridization (ISH)** uses labeled complementary DNA or RNA probes (riboprobes) that hybridize directly to specific target mRNA sequences within fixed whole-mount embryos or histological tissue sections. This preserves the 3D histological architecture, directly pinpointing which cells express the transcript (spatial resolution) across various stages of development (temporal resolution).
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: Northern blotting analyzes RNA isolated from bulk homogenized tissue; cellular and spatial tissue architecture is completely destroyed during extraction.
- **Option (B) [CORRECT]**: In situ hybridization allows microscopic, direct visualization of RNA transcripts within intact specimens, providing both spatial and temporal expression profiles.
- **Option (C) [INCORRECT]**: Southern blotting detects DNA fragments, not RNA transcripts, and also requires bulk tissue homogenization.
- **Option (D) [INCORRECT]**: Western blotting detects proteins, not RNA transcripts, and operates on cell/tissue lysates without spatial context.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: +1.0 Mark (Negative marking: -0.33 marks).
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