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.
The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Elution
After the gel run, each band of DNA holds fragments of one size. The band is cut out with a blade, and the DNA is taken out of the gel piece.
(1) Extraction — Incorrect. This is a general word. It is not the name given to taking DNA out of a gel piece.
(2) Separation — Incorrect. Separation is the step in which the fragments move through the gel and form bands according to their size. It comes before the cutting.
(3) Isolation — Incorrect. Isolation is the step of getting DNA out of the cells in the first place.
(4) Elution — Correct. Cutting the bands out of the agarose gel and extracting the DNA from the gel piece is called elution. The purified fragments can then be joined to a cloning vector.
Note: 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.
NCERT Extract:
Restriction Enzymes – …
