In agarose gel electrophoresis, the separated DNA fragments can be visualised by staining the DNA with a compound, known as -
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Ethidium bromide
DNA fragments in an agarose gel are invisible. They are seen only after staining the gel with ethidium bromide and exposing it to UV light, when the DNA shows as bright orange bands.
Option (3) Ethidium bromide — Correct. It is the stain NCERT names for seeing DNA bands under UV light.
Note: The same question was also asked in CUET (UG) 2025 on 20-05-2025 (Slot 2), and a similar question in CUET (UG) 2026 on 31-05-2026 (Slot 2) and on 20-05-2026 (Slot 2), and in CUET (UG) 2025 on 16-05-2025 (Slot 1).
NCERT Extract:
Restriction Enzymes – “… 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 a ethidium bromide stained gel exposed to UV light (Figure 9.3).”
Figure 9.3 A typical agarose gel electrophoresis showing migration of undigested (lane 1) and digested set of DNA fragments (lane 2 to 4)