Question

Which of the following represents the correct sequence of steps in recombinant DNA technology?

I. Isolation of the DNA fragment or genes
II. Introduction of rDNA into the host
III. Expression of the introduced gene in the host
IV. Selection and identification of the transformed host
V. Insertion of the isolated gene in a suitable vector

• A. I→ III → II → IV → V
• B. III → II → I → V → IV
• C. I → V → II → IV → III
• D. V → I → III → IV → II

Answer 1

The correct option is C I → V → II → IV → III

Recombinant DNA technology is the set of techniques which enables the DNA from varied sources to be identified, isolated and recombined so that new characteristics can be introduced into an organism. Following steps are involved in the recombinant DNA technology:

1. DNA containing the gene of interest is identified and isolated from the organism
2. The gene of interest is inserted into the plasmid which is a vector which is used to deliver and maintain the DNA in the host organism. This is known as recombinant DNA or rDNA
3. The rDNA is now introduced into the host and the process is known as transformation. Here, several vector-based and vectorless methods are used in this process of transfer
4. The host cells that have taken up the rDNA are known as transformed cells. These cells need to be differentiated from the other cells that have not taken up the rDNA. Here, growing the mixture of cells in an antibiotic-containing medium helps in the selection and identification of the transformants from the non-transformants. The various selectable markers also play an important role in identifying the recombinants from the non-recombinants
5. The rDNA containing the gene of interest expresses itself by producing a protein and this is known as the expression of the introduced gene

Hence, I → V → II → IV → III is the correct order of events.