25. Which one of the following microscopes would you use to visualize a protein fused to an appropriate reporter in a living cell?
A. Fluorescence microscope
B. Scanning electron microscope
C. Differential interference contrast microscope
D. Phase contrast microscope
Fluorescence microscopy is the only technique capable of visualizing proteins fused to reporters like GFP in living cells.
Correct Answer
A. Fluorescence microscope. Reporter fusions (GFP, RFP, YFP) emit light at specific wavelengths detectable only by fluorescence excitation/emission optics.
Option Breakdown
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A. Fluorescence microscope: Correct. Excites fluorescent reporters (488 nm → 509 nm GFP) in live cells for specific protein localization/dynamics.
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B. Scanning electron microscope: Incorrect. Surface imaging via electron scattering; cannot detect fluorescent proteins or image live cells.
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C. Differential interference contrast microscope: Incorrect. DIC enhances contrast via phase gradients; blind to fluorescence signals.
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D. Phase contrast microscope: Incorrect. Phase contrast reveals refractive index differences; cannot visualize fluorescent reporters.
Protein fused reporter living cell microscope choice is fluorescence microscopy – the gold standard for GFP/RFP visualization in dynamic cellular processes.
Reporter mechanism: Protein-GFP fusion → 488 nm excitation → 509 nm emission → specific detection via emission filters. Live cell compatible, no fixation required.
Technique Comparison Table
| Microscope | Live Cells | Sees Reporters | Principle | GATE Choice |
|---|---|---|---|---|
| Fluorescence | Yes | GFP/RFP | Excitation/Emission | Correct |
| SEM | No | No | Electron scattering | Surface only |
| DIC | Yes | No | Phase gradients | Contrast only |
| Phase Contrast | Yes | No | Phase shifts | Unstained cells |
Key specs: 40x/1.3NA oil objective + 488 nm laser + 500-550 nm emission filter = optimal live cell imaging.
Live Cell Applications
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Actin dynamics: LifeAct-GFP treadmilling
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Membrane trafficking: Rab5-GFP endosomes
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Mitosis: Histone2B-mCherry chromosomes
Exam Memory Aid: Reporter = Fluorescence only. Phase/DIC see all cells; fluorescence sees tagged cells only.
