Tools of Biotechnology
Read the following passage carefully and answer the given questions.
It is evident that genetic engineering or recombinant DNA technology can be accomplished only if we have the key tools, i.e., restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. DNA fragments are negatively charged molecules which can be separated by forcing them to move towards the anode under an electric field through a medium. Nowadays the most commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments are resolved according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves. If the process of replication of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times. Such repeated amplification is achieved by the use of a thermostable DNA polymerase, which remain active during high temperature.
Which one of the following techniques is used to separate the bands of DNA?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Agarose gel electrophoresis
DNA fragments carry a negative charge. In an electric field they move towards the anode through a gel of agarose, which is a natural polymer from sea weeds. The gel works like a sieve, so smaller fragments move farther. Fragments of different sizes therefore form separate bands.
(1) Agarose gel electrophoresis — Correct. It separates the DNA fragments by their size.
(2) PCR — Incorrect. PCR (polymerase chain reaction) makes many copies of a DNA segment. It does not separate bands.
(3) ELISA — Incorrect. ELISA (enzyme linked immuno-sorbent assay) detects an antigen or an antibody by their binding. It is not used to separate DNA.
(4) Autoradiography — Incorrect. This detects a radioactive probe on a film. It does not separate DNA.
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: A similar question was also asked in CUET (UG) 2026 on 29-05-2026 (Slot 1), and in CUET (UG) 2025 on 28-05-2025 (Slot 1) and on 23-05-2025 (Slot 2).
NCERT Extract:
Restriction Enzymes – …
