Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Which one of the following techniques can be used to compare the expression of a large
number of genes in two biological samples in a single experiment?
Options:
(A) Polymerase chain reaction
(B) DNA microarray
(C) Northern hybridization
(D) Southern hybridization
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.18)**
**1. Governing Concept**:
- **Topic**: Functional Genomics & Transcriptome Profiling
- To compare the simultaneous expression levels of thousands of genes between two biological samples (e.g., normal tissue vs. cancerous tumor) in a single experimental run, **DNA microarray** technology is uniquely tailored:
- Two biological RNA samples are reverse-transcribed into cDNAs labeled with distinct fluorophores (e.g., Cy3-green and Cy5-red).
- Competitive co-hybridization to high-density spotted cDNA/oligonucleotide probes across the array simultaneously measures the differential expression of thousands of transcripts.
- Northern blotting, RT-PCR, and Southern blotting typically analyze individual single genes/transcripts.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Standard PCR amplifies single loci.
- **Option (B) [DNA microarray] is CORRECT**: High-throughput hybridization platform designed for genome-wide differential expression profiling.
- **Option (C) is INCORRECT**: Northern blotting analyzes one specific RNA transcript per membrane probe.
- **Option (D) is INCORRECT**: Southern blotting detects DNA genomic fragments, not expression levels.
**3. Final Answer**:
- **Correct Choice**: **B**
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