Read the following passage carefully and answer the given questions.
The separated DNA fragments can be visualized only after staining the DNA with ethidium bromide followed by exposure to UV radiation. Bright orange colored bands of DNA in ethidium bromide stained gel exposed to UV light can be seen. 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 a cloning vector.
The extraction of separated bands of DNA from the gel piece is called:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Elution
Option (1) Elution — Correct. After electrophoresis, the band that holds the wanted DNA is cut out of the agarose gel. Taking the DNA out of this gel piece is elution. The purified DNA is then joined to a cloning vector.
Option (2) Cloning — Incorrect. Cloning means making many identical copies of a DNA molecule, usually by letting it multiply inside a host cell. It comes after the DNA is purified and joined to a vector.
Option (3) Transformation — Incorrect. Transformation is the process by which a piece of DNA is introduced into a host bacterium. It has nothing to do with taking DNA out of a gel.
Option (4) Replication — Incorrect. Replication is the copying of DNA inside a cell before the cell divides. It is a natural process of the cell, not a laboratory step.
Note 1: This passage is taken from NCERT as it is. 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) 2023 on 31-05-2023 (Slot 3).