(i): The construction of 1st recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid of Salmonella typhemunium.
Process of rDNA technology:
It starts with the selection of the desired gene for administration into the host followed by a selection of perfect vector, with which the gene has to be integrated and recombinant DNA formed.
This rDNA , then has to be introduced into the host.
Finally, it has to be maintained in the host and carried forward to the offsprings.
Detail description of the process:
1. Isolation of DNA: it is an enzymatically controlled process where the plant or animal cell are treated with certain enzymes, like cellulase, lysozyme and chitinase.
2. Fragmentation of DNA: The isolated and purified DNA is treated with restriction endonucelases which cut the DNA into fragments.The restriction enzymes play a major role in determining the location at which the desired gene is inserted into the vector genome.
The restriction endonucleases are sequence-specific and cut the DNA at specific points.They scrutinise the length of DNA and make a cut at specific site called the Restriction site.
3. Amplification of gene of interest: PCR(polymerase chain reaction) is the process to amplify the gene, once the proper gene of interest has been cut using the restriction enzyme.
By this process multiple copies of gene of interest can be produced.
PCR consists 3 stages : Denaturation, Annealing and Extension.
4. Insertion of rDNA into the host: the host is the main tool of rDNA technology, which takes in the vector engineered with the desired DNA with the help of the enzymes. Insertion of desired rDNA into host can be don in many ways. This includes, microinjection, biolistics or the gene gun, alternating heating and cooling, use of calcium ions…….etc
The successfully transformed organisms carry forward the recombinant gene to the offsprings.
(ii) rDNA was first constructed Stanley Cohen and Herbert Boyer in the year 1972.
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