Biotechnology: Principles and Processes — BIOLOGY STD 12 Science — Question

The technique in which recombinant DNA is obtained by introducing the DNA of one species into the DNA of another species is called genetic engineering.
In genetic engineering, recombinant DNA is created using gene cloning and gene transfer. The first recombinant DNA was created by adding an antibiotic-resistant transcription gene to the plasmid of Salmonella typhimarium. Stanley Cohen and Herbert Boyer’s work was accomplished in 1972 by cutting a piece of DNA from a plasmid, which contained the gene responsible for providing antibiotic resistance. The discovery of 'restriction enzymes' called molecular scissors made it possible to cut DNA at specific places. The cut DNA portion is combined with the plasmid DNA. This plasmid acts as a DNA vector which transfers the DNA attached to it. The work of connecting the antibiotic resistance gene with the vector is done by the enzyme DNA ligase, which works on the cut part of the DNA molecule and joins its ends. By this combination, new circular self-replicating DNA is formed in vitro, which is called recombinant DNA. When this DNA is transferred into Escherichia coli, it makes multiple copies by using the DNA polymerase enzyme of the new host.