Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Which of the following methods are used for detection of DNA and RNA,
respectively?
Options:
(A) Southern and Northern blotting
(B) Southern and Western blotting
(C) Northern and Southern blotting
(D) Northern and Western blotting
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.24)**
**1. Governing Concept**:
- **Topic**: Molecular Biology Techniques & Macromolecular Blotting
- Canonical macromolecular blotting nomenclature:
- **Southern blot**: Detection of specific **DNA** sequences using complementary DNA/RNA probes (invented by Edwin Southern).
- **Northern blot**: Detection of specific **RNA** transcripts (gene expression levels).
- **Western blot**: Detection of specific **proteins** using antibodies.
- **Eastern blot**: Detection of post-translational modifications (e.g., carbohydrates/lipids).
**2. Option Analysis**:
- **Option (A) [Southern and Northern blotting] is CORRECT**: DNA is detected by Southern blot, and RNA is detected by Northern blot.
- **Option (B) is INCORRECT**: Western blotting detects proteins.
- **Option (C) is INCORRECT**: Inverts the order of DNA and RNA.
- **Option (D) is INCORRECT**: Northern detects RNA, Western detects proteins.
**3. Final Answer**:
- **Correct Choice**: **A**
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