Read the passage and answer the following questions:
In almost all recombinant technologies, the ultimate aim is to produce a desirable protein. Hence, there is a need for the recombinant DNA to be expressed. The foreign gene gets expressed under appropriate conditions. After having cloned the gene of interest and having optimised the conditions to induce the expression of the target protein, one has to consider producing it on a large scale. The cells harbouring cloned genes of interest may be grown on a small scale in the laboratory. The cultures may be used for extracting the desired protein and then purifying it by using different separation techniques. Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities, the development of bioreactors, where large volumes of culture can be processed, was required. The most commonly used bioreactors are of stirring type.
Arrange the following steps of obtaining a recombinant protein in the correct sequence:
A. The product is separated and purified by downstream processing.
B. The gene of interest is cloned.
C. The conditions to induce the expression of the target protein are optimised.
D. The cells are cultured on a large scale in a bioreactor.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → B, C, D, A
The steps follow the path from gene to finished product. The passage states that only after having cloned the gene of interest and having optimised the conditions to induce the expression of the target protein does one consider producing it on a large scale, in bioreactors. Separation and purification come at the very end.
B. The gene of interest is cloned. — First. Nothing can be expressed until the gene is in the host and multiplied.
C. The conditions to induce the expression of the target protein are optimised. — Second. The foreign gene is expressed only under appropriate conditions, and these are worked out on the cloned gene.
D. The cells are cultured on a large scale in a bioreactor. — Third. Small cultures cannot give appreciable quantities, so the cells are scaled up. This is the biosynthetic stage.
A. The product is separated and purified by downstream processing. — Fourth. The product can be separated and purified only after it has been made, that is, after the biosynthetic stage is complete.
NCERT Extract:
Downstream Processing – “After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it is ready for marketing as a finished product. The processes include separation and purification, which are collectively referred to as downstream processing. The product has to be formulated with suitable preservatives.”