Question

Which of the following tools of recombinant DNA technology is incorrectly paired with its use?
A. Reverse transcriptase- production of cDNA from mRNA
B. DNA polymerase- used in polymerase chain reaction to amplify section of DNA
C. DNA ligase- enzyme that cuts DNA, creating the sticky ends of restriction fragments
D. Restriction enzymes- production of RFLPs

Answer 1

Hint:- Use of organisms or their components or products to produce products and services which are useful for human beings is called biotechnology.
Modern biotechnology is based on two types of techniques named- genetic engineering and chemical engineering.
Genetic engineering includes all the techniques to alter the chemistry of genetic material, to introduce these into host organisms and thus change the phenotype of an organism.

Complete answer:- Genetic engineering or recombinant DNA technology can be accomplished only with the help of some key tools which are- restriction enzymes, polymerase enzymes, ligases, vectors, and the host organisms.
During transcription, RNA is formed from DNA but the process of formation of DNA from RNA is called reverse transcription. The enzyme reverse transcriptase is used in this process. In this process, single-stranded RNA is produced by double-stranded DNA in the host's cell with this enzyme. It is called cDNA (complementary DNA).
DNA polymerase is the enzyme that is used during DNA replication. During polymerase chain reaction, multiple copies of the gene of interest (DNA) are synthesized in vitro using enzyme DNA polymerase. In this reaction the process of DNA replication is repeated many times.
When the genome of two individuals is cut by using the same restriction enzymes, the length of restriction fragments obtained for both individuals will be different. This phenomenon is called RFLP (restricted fragment length polymorphism).
DNA ligases are the enzymes used for joining of the DNA fragments which have been cut by restriction endonucleases. Restriction endonucleases cut the DNA strand at a distance away from the centre of the palindromic site. This leaves single-stranded portions at the end (sticky ends), which facilitates the action of DNA ligases.

Thus the correct answer is option (C)

Note:- The cDNA produced during reverse transcription remains shorter than actual gene due to lack of introns. Repeated amplification of DNA during PCR technique is achieved by the use of a thermostable DNA polymerase.
Variations occurring in the base sequence of DNA in different individuals are different. So RFLPs are obtained.
When cut by the same restriction enzyme, the resultant DNA fragments have the same kind of sticky ends and these can be joined together in an end to end fashion using DNA ligases. These DNA ligases are also called 'molecular glues'.