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 is not a step of polymerase chain reaction?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Transformation
In PCR the DNA is copied again and again in a test tube. Each cycle has three steps, and the cycle is repeated many times. A heat-stable DNA polymerase does the copying.
(1) Extension — A step of PCR. The polymerase adds nucleotides to the primers and builds the new strands.
(2) Transformation — Not a step of PCR. Transformation is the entry of recombinant DNA into a host cell. It is done after the DNA has been cut and joined, and it takes place in cells, not in the PCR tube.
(3) Denaturation — A step of PCR. High temperature separates the two strands of the DNA.
(4) Annealing — A step of PCR. The primers join the separated strands at their matching places.
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.