Q.41 Match the item in Column I with the corresponding technique in Column II.
Column I                                          Column II
P. Blue laser                                    1. Electron microscopy
Q. Tungsten filament                    2. Fluorescence activated cell sorting
R. 15N labelled protein                 3. Electrophoresis
S. Polyacrylamide                           4. Nuclear magnetic resonance spectroscopy
(A) P-2; Q-3; R-1; S-4
(B) P-2; Q-1; R-4; S-3
(C) P-3; Q-1; R-4; S-2
(D) P-1; Q-2; R-4; S-3

Discover the right match for Blue laser, Tungsten filament, 15N labelled protein, and Polyacrylamide in advanced biology techniques. This SEO-optimized guide breaks down the MCQ with expert explanations for exam prep in genetics, biochemistry, and molecular biology.

Understanding the Question

This multiple-choice question tests knowledge of key instruments and techniques in biological sciences, linking specific components (Column I) to their primary applications (Column II). These tools are essential in molecular biology, biochemistry, and cell analysis—fields central to research in genetics and microbiology.

Column I items represent hardware or reagents:

• P. Blue laser: A light source at ~405-488 nm wavelength.

• Q. Tungsten filament: A heated metal wire emitting electrons.

• R. 15N labelled protein: Protein enriched with nitrogen-15 isotope.

• S. Polyacrylamide: A polymer gel matrix.

Column II lists techniques:

1. Electron microscopy

2. Fluorescence activated cell sorting (FACS)

3. Electrophoresis

4. Nuclear magnetic resonance spectroscopy (NMR)

The task matches each P-Q-R-S to 1-2-3-4 correctly.

Correct Answer and Matching

The correct option is (B) P-2; Q-1; R-4; S-3.

Here’s the precise matching with reasoning grounded in scientific principles:

• P. Blue laser → 2. Fluorescence activated cell sorting (FACS)
  FACS uses lasers, often blue (e.g., 488 nm argon-ion or solid-state equivalents), to excite fluorescent dyes on cells. The laser interrogates cells in a fluid stream, enabling sorting based on fluorescence signals. This is standard in cell biology for isolating genetically modified populations.

• Q. Tungsten filament → 1. Electron microscopy
  In transmission electron microscopes (TEM) and scanning electron microscopes (SEM), a tungsten filament serves as the electron gun’s cathode. It thermionically emits electrons when heated, forming the high-resolution electron beam for imaging ultrastructures like plant cell walls or microbial membranes.

• R. 15N labelled protein → 4. Nuclear magnetic resonance spectroscopy (NMR)
  15N labeling provides isotopic enrichment for NMR, enhancing signal sensitivity in protein structure determination. Natural 14N has poor NMR properties (quadrupolar nucleus), so 15N (spin-1/2) enables multidimensional NMR experiments like HSQC to map protein backbones—crucial in structural biochemistry.

• S. Polyacrylamide → 3. Electrophoresis
  Polyacrylamide gels (e.g., PAGE or SDS-PAGE) act as sieving matrices in electrophoresis, separating proteins or DNA by size and charge under electric fields. This is foundational for analyzing gene products in plant genetics or enzyme kinetics studies.

Why Other Options Are Incorrect

Each wrong choice misaligns at least one item, highlighting common pitfalls in technique recall:

Option (A) P-2; Q-3; R-1; S-4

• Correct: P-2 (FACS).

• Wrong: Q-3 (Tungsten not for electrophoresis; that’s gel-based). R-1 (15N not for EM; EM uses heavy metals like osmium). S-4 (Polyacrylamide irrelevant to NMR).
  This confuses imaging with separation and spectroscopy.

Option (C) P-3; Q-1; R-4; S-2

• Correct: Q-1 (EM), R-4 (NMR).

• Wrong: P-3 (Blue laser powers FACS optics, not electrophoresis). S-2 (Polyacrylamide separates in gels, not FACS which is flow-based).
  Errors stem from mixing optical/flow cytometry with gel electrophoresis.

Option (D) P-1; Q-2; R-4; S-3

• Correct: R-4 (NMR), S-3 (electrophoresis).

• Wrong: P-1 (Blue laser is visible light; EM uses electrons). Q-2 (Tungsten emits electrons, not suited for FACS lasers).
  This swaps electron sources with laser/photon tech.

Applications in Biological Research

These matches reflect real-world uses: FACS for sorting fluorescently tagged plant immune cells, EM for visualizing microbial biofilms, NMR for 15N-labeled enzyme structures in biochemistry, and PAGE for purity-checking genetically modified proteins.