Molecular Biology Techniques in Microbiology — MCQs

Q: What does Polymerase Chain Reaction (PCR) detect?

Nucleic acid. **Explanation:** **Why Nucleic Acid is the Correct Answer:** Polymerase Chain Reaction (PCR) is a molecular technique used to **amplify specific sequences of DNA**. It utilizes a heat-stable DNA polymerase (like *Taq* polymerase) to create millions of copies of a target genetic sequence. In microbiology, PCR is used to detect the **nucleic acid** (DNA or RNA) of a pathogen. For RNA viruses (like HIV or SARS-CoV-2), a variation called Reverse Transcription-PCR (RT-PCR) is used to first convert RNA into complementary DNA (cDNA) before amplification. **Why Other Options are Incorrect:** * **Antigens (Option A):** These are proteins or polysaccharides on the surface of a pathogen. They are detected using immunological assays like **ELISA** (Enzyme-Linked Immunosorbent Assay) or Lateral Flow Assays (Rapid Antigen Tests), not PCR. * **Antibodies (Option B):** These are host proteins produced by B-cells in response to an infection. They are detected via **Serology** (e.g., ELISA, Western Blot, or Agglutination tests) to identify past or current exposure, whereas PCR identifies the presence of the organism itself. **High-Yield Clinical Pearls for NEET-PG:** * **Steps of PCR:** Denaturation (94-96°C) → Annealing (50-65°C) → Extension (72°C). * **Real-Time PCR (qPCR):** Allows for **quantification** of the microbial load (e.g., Viral Load in Hepatitis C or HIV). * **Multiplex PCR:** Can detect multiple different pathogens in a single clinical sample simultaneously using different primers. * **Sensitivity:** PCR is highly sensitive, making it the "Gold Standard" for diagnosing organisms that are difficult to culture (e.g., *M. tuberculosis*, *Chlamydia*, or viral infections).

Molecular Biology Techniques in Microbiology — MCQs

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Nucleic Acid Extraction Methods

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Polymerase Chain Reaction

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Real-Time PCR

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DNA Sequencing Techniques

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Next-Generation Sequencing in Microbiology

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Pulsed-Field Gel Electrophoresis

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Whole Genome Sequencing

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MALDI-TOF Mass Spectrometry

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Microarrays in Microbial Diagnostics

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Molecular Typing Methods

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Bioinformatics Tools in Microbiology

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Metagenomics

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