DNA Visualization: Ethidium Bromide Staining — NEET Biology
✅ Asked in NEET 2026Which statements are correct with respect to DNA separation, isolation and visualization? A. Cutting of DNA is by molecular scissors. B. DNA fragments separate by size in agarose gel during electrophoresis. C. Separated DNA fragments can be seen without staining when exposed to UV. D. DNA stained with ethidium bromide is visible in visible light.
Which statements are correct with respect to DNA separation, isolation and visualization? A. Cutting of DNA is by molecular scissors. B. DNA fragments separate by size in agarose gel during electrophoresis. C. Separated DNA fragments can be seen without staining when exposed to UV. D. DNA stained with ethidium bromide is visible in visible light.
Identify the incorrect statement related to electrophoresis: (NEET 2024)
Upon exposure to UV radiation, DNA stained with ethidium bromide will show: (NEET 2023)
In gel electrophoresis, separated DNA fragments can be visualized with the help of: (NEET 2020)
The DNA fragments separated on an agarose gel can be visualised after staining with: (NEET 2017)
Answer & NCERT explanation
Correct answer: B — A and B only
Restriction enzymes (molecular scissors) cut DNA, and fragments separate by size in agarose gel. DNA cannot be seen unstained — visualisation needs ethidium bromide staining and UV exposure (so C and D are wrong as stated).
Read more NCERT concept on the PYQ
The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation (you cannot see pure DNA fragments in the visible light and without staining). You can see bright orange coloured bands of DNA in an ethidium bromide stained gel exposed to UV light. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution. The DNA fragments purified in this way are used in constructing recombinant DNA by joining them with cloning vectors.
NTA tests whether students understand that pure DNA fragments cannot be seen under visible light and must be stained with ethidium bromide, then exposed to UV radiation to visualize them as bright orange bands. The common mistake is thinking DNA can be seen directly under a microscope without staining, or confusing ethidium bromide with other gel dyes. Remember: DNA itself is colorless and invisible → ethidium bromide intercalates into DNA → UV excitation produces orange fluorescence. This concept appears repeatedly because gel electrophoresis visualization is fundamental to recombinant DNA technology, and understanding the detection method is essential for practical molecular biology.
What does NCERT say about separated DNA fragments can?
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