Match the item in Column I with the corresponding technique in Column II.
Column I
P. Blue laser
Q. Tungsten filament
R. N labelled protein
S. Polyacrylamide
Column II
1. Electron microscopy
2. Fluorescence activated cell sorting
3. Electrophoresis
4. Nuclear magnetic resonance spectroscopy
P-2; Q-3; R-1; S-4
P-2; Q-1; R-4; S-3
P-3; Q-1; R-4; S-2
P-1; Q-2; R-4; S-3
ANSWER
The correct answer is (B) P-2; Q-1; R-4; S-3.
Official answer: BSource: Official answer key, GATE 2024 BT (IISc Bengaluru)
P. Blue laser: FACS instruments use a laser (typically 488 nm, blue) to excite fluorophore-tagged cells as they flow single-file past the detector, so P pairs with technique 2 (Fluorescence Activated Cell Sorting).
Q. Tungsten filament: In a conventional electron microscope, the tungsten filament is the thermionic electron gun that generates the electron beam used for imaging, so Q pairs with technique 1 (Electron microscopy).
R. N labelled protein: N is an NMR-active isotope, and isotopic labelling of recombinant proteins with N is the standard way to enable multidimensional heteronuclear NMR studies of protein structure, so R pairs with technique 4 (Nuclear magnetic resonance spectroscopy).
S. Polyacrylamide: Polyacrylamide gels are the standard matrix used to separate proteins and nucleic acids by size under an applied electric field, so S pairs with technique 3 (Electrophoresis).
Combining: P-2; Q-1; R-4; S-3, which matches option (B) exactly.
Check other options: (A) has Q-3 (a tungsten filament is not used in electrophoresis) — wrong. (C) has P-3 (a laser is not used for electrophoresis) — wrong. (D) has P-1 and Q-2 (a laser is not the EM electron source, and a filament is not the FACS excitation source) — wrong.
Only (B) has all four pairings independently correct, so the answer is (B).
KEY IDEA
Match each physical component/label to the biophysical technique that relies on it: a blue (488 nm) laser excites fluorophores in FACS; a tungsten filament is the thermionic electron source in electron microscopy; N isotope labelling enables multidimensional NMR of proteins; polyacrylamide gels are the standard matrix for electrophoretic separation.
WATCH OUT FOR
Confusing which physical component belongs to which technique — e.g., assuming a laser is used in electron microscopy (it isn't; EM uses an electron beam from a filament) or that polyacrylamide is used in NMR rather than electrophoresis.
From the GATE 2024 BT paper. Every question of this paper · Download the full paper · All 8 Microscopy & spectroscopy questions, with notes
