Flow cytometry is the standard technique for measuring DNA content in cell nuclei, as confirmed in this multiple-choice question. This SEO-optimized article explains the correct answer and all options for students in molecular biology and biotechnology.​

Correct Answer

The correct option is (C) Flow Cytometry.
Flow cytometry quantifies DNA in individual cell nuclei by staining with fluorescent dyes like propidium iodide, then analyzing thousands of cells via laser-based detection for precise DNA content, cell cycle phases, and ploidy.
This method excels in high-throughput analysis, detecting sub-G1 apoptotic cells or aneuploidy, making it ideal for research and diagnostics.

Option Breakdown

ESR Spectroscopy

Electron Spin Resonance (ESR) detects unpaired electrons in paramagnetic samples, used for free radical studies or spin-labeling in membranes.
It cannot measure DNA content, as DNA lacks inherent paramagnetic properties for direct quantification.​

FTIR Spectroscopy

Fourier Transform Infrared (FTIR) identifies molecular vibrations for chemical composition, like protein secondary structure or lipid analysis.
FTIR provides indirect nucleic acid signatures but lacks single-nucleus resolution or quantitative DNA staining capability.​

Flow Cytometry

Flow cytometry passes nuclei through a laser beam after DNA-specific fluorochrome staining (e.g., DAPI, PI), measuring fluorescence proportional to DNA amount.
It generates histograms for G0/G1, S, G2/M phases, with low CV at optimal flow rates (<1000 cells/sec).​

X-Ray Crystallography

X-ray crystallography determines atomic structures of crystallized macromolecules, like DNA-protein complexes (e.g., nucleosome).
It requires purified crystals and reveals static 3D models, not bulk or single-nucleus DNA content measurement.​

Why Flow Cytometry Wins

For biotech exams, prioritize flow cytometry for DNA content queries—practice with PI staining protocols.