Q.18 Match the entries in Group I with the entries in Group II
| Group I | Group II |
|---|---|
| P) Yeast 2 Hybrid System | 1) in vivo protein-DNA interaction |
| Q) Electrophoretic Mobility Shift Assay | 2) protein structure determination |
| R) Chromatin Immunoprecipitation | 3) in vitro protein-DNA interaction |
| S) Nuclear Magnetic Resonance | 4) protein-protein interaction |
The correct matching is: P–4, Q–3, R–1, S–2, so the right option is (C).
Introduction
Understanding how different molecular biology techniques map protein–protein and protein–DNA interactions is essential for CSIR NET and other life‑science exams. This article explains Yeast Two Hybrid System, Electrophoretic Mobility Shift Assay, Chromatin Immunoprecipitation and Nuclear Magnetic Resonance, and shows how to match them with the correct applications in Group II.
Matching of techniques
| Group I method | Correct Group II entry | Explanation (exam‑oriented) |
|---|---|---|
| P) Yeast 2 Hybrid System | 4) protein–protein interaction | Detects interacting protein pairs in vivo using bait and prey fusion constructs that reconstitute a transcription factor only when they bind. |
| Q) Electrophoretic Mobility Shift Assay | 3) in vitro protein–DNA interaction | EMSA (gel‑shift assay) mixes purified protein with labeled DNA/RNA and detects binding by slower migration of the complex on native gel. |
| R) Chromatin Immunoprecipitation | 1) in vivo protein–DNA interaction | ChIP crosslinks proteins to DNA in living cells, immunoprecipitates the protein of interest, and identifies associated genomic regions. |
| S) Nuclear Magnetic Resonance | 2) protein structure determination | NMR spectroscopy provides atomic‑resolution three‑dimensional structures and dynamics of proteins in solution or membranes. |
Thus: P–4, Q–3, R–1, S–2 → Option (C).
Why other options are wrong
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Option (A) P–3, Q–2, R–1, S–4
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Assigns EMSA (Q) to structure determination, which is incorrect because EMSA only shows binding of nucleic acids and proteins, not structure.
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P–3 would wrongly treat Yeast Two Hybrid as a protein–DNA assay, whereas it specifically detects protein–protein interactions via reporter activation.
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Option (B) P–4, Q–3, R–1, S–2
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This matches every method correctly, so it is conceptually right; however in the question’s labeled choices this pattern corresponds to option (C), not (B), so option (B) as printed with a different order would be inconsistent.
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Option (D) P–1, Q–3, R–4, S–2
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P–1 suggests Yeast Two Hybrid measures in vivo protein–DNA interaction, but it detects protein–protein binding mediated by a DNA‑binding domain, not direct DNA recognition.
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R–4 assigns ChIP to protein–protein interaction, whereas ChIP pulls down chromatin to map protein–DNA contacts on the genome.
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Brief notes on each technique
Yeast Two Hybrid System
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Used for genome‑wide or targeted screening of protein partners inside yeast cells.
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Relies on reconstitution of a split transcription factor when bait and prey proteins interact, leading to reporter gene expression.
Electrophoretic Mobility Shift Assay (EMSA)
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An in vitro binding assay that detects protein–DNA or protein–RNA complexes as shifted bands on a native gel.
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Useful for determining binding affinity, competition, and specificity using purified or nuclear‑extract proteins.
Chromatin Immunoprecipitation (ChIP)
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Captures in vivo association of transcription factors or histone modifications with specific genomic regions after crosslinking in intact cells.
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Downstream analysis by PCR, qPCR or sequencing identifies target promoters and regulatory elements.
Nuclear Magnetic Resonance (NMR) Spectroscopy
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Provides high‑resolution three‑dimensional structures and dynamic information for proteins, especially in solution.
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Widely used alongside crystallography in structural biology and drug‑design studies.
