Read the Passage carefully and answer the questions.
The DNA fragments can be separated by a technique known as gel electrophoresis. Since DNA fragments are negatively charged molecules, they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. 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. The repeated amplification of DNA is achieved by the use of a thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus). After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it is ready for marketing as a finished product. The downstream processing and quality control testing vary from product to product. The convention for naming restriction enzymes is the first letter of the name comes from the genus and the second two letters come from the species of the prokaryotic cell from which they were isolated.
In agarose gel electrophoresis, the DNA fragments can be visualised only after 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 1: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
Note 2: The same question was also asked in CUET (UG) 2025 on 14-05-2025 (Slot 1), 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).