Recombinant DNA technology
Read the following passage carefully and answer the given questions
Biotechnology has been used by humans since times immemorial in the form of unmodified microbe mediated processes. However, rDNA technology uses genetically modified organisms and employs number of tools. The key tools are restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. Restriction enzymes are also called as nucleases as they cut the DNA. Exonucleases cuts the DNA from the ends whereas endonucleases cuts the DNA at specific positions within the DNA. Endonucleases recognize a sequence of six base pairs called ‘recognition sequence’. Restriction enzymes cut both foreign DNA and vector DNA at specific point. Plasmids and bacteriophages are the commonly used vectors for transferring rDNA into the host organism. Vectors used now a days are engineered in such a way that help in easy linking with foreign DNA as well as selection of recombinants from non-recombinants. Maintenance of introduced DNA in the host and transfer of DNA to its progeny is one of the basic step of biotechnology.
Which one of the following enzymes is not used in cloning of rDNA?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → RNA polymerase
Cloning an rDNA needs tools that cut DNA, join DNA and copy DNA.
(1) DNA ligase — An enzyme used in cloning of rDNA. It joins the cut ends of the vector and the foreign DNA.
(2) DNA polymerase — An enzyme used in cloning of rDNA. It copies DNA, for example when the gene of interest is multiplied by PCR before it is cloned.
(3) Restriction endonuclease — An enzyme used in cloning of rDNA. It cuts the vector and the foreign DNA at specific sites.
(4) RNA polymerase — Not an enzyme used in cloning of rDNA. It makes RNA from a DNA template during transcription. It is not a tool for cutting, joining or copying DNA in cloning.
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.