GATE BT 2025 • Q55
MSQ • 2 Marks
Section 4: Bioprocess Engineering and Process Biotechnology
Downstream processing (chromatography, filtration)
Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Which of the following methods is/are used for identifying histone modifications?
Options:
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(A) ChIP-seq
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(B) Mass spectrometry
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(C) Immunofluorescence
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(D) Patch-clamp electrophysiology
Official Answer Key:
A;B;C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.55)**
**1. Governing Concept**:
- **Topic**: Epigenetics & Analytical Methods for Post-Translational Modifications
- Analysis of histone post-translational modifications (methylation, acetylation, phosphorylation) requires high-specificity molecular and proteomic techniques:
1. **Chromatin Immunoprecipitation (ChIP / ChIP-seq)**: Uses modification-specific antibodies (e.g. anti-H3K4me3, anti-H3K27ac) to map genomic locations of histone marks.
2. **Mass Spectrometry (LC-MS/MS)**: Directly detects mass shifts corresponding to covalent PTMs (e.g. +42 Da for acetylation, +14 Da for methylation).
3. **Western Blotting**: Uses epitope-specific antibodies targeting modified histone residues.
- Conversely, Northern blotting detects RNA transcripts and cannot detect protein covalent modifications.
**2. Option Analysis**:
- **Option (A) [Mass spectrometry] is CORRECT**: Gold-standard method for identifying specific covalent mass additions on histone peptides.
- **Option (B) [Chromatin Immunoprecipitation (ChIP)] is CORRECT**: Standard method for profiling histone PTM distribution across chromatin.
- **Option (C) [Western blotting] is CORRECT**: Uses modification-specific antibodies to detect and quantify histone marks.
- **Option (D) [Northern blotting] is INCORRECT**: Used exclusively for RNA size separation and expression detection.
**3. Final Answer**:
- **Correct Options**: **A, B, C**
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