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.
Choose the correct statements from the following:
A. If any protein encoding gene is expressed in a heterologous host, it is called a recombinant protein.
B. Bioreactors are vessels in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial, plant, animal or human cells.
C. A bioreactor provides optimum growth conditions such as temperature, pH, substrate, salts, vitamins and carbon dioxide for achieving the desired product.
D. In a continuous culture system, the used medium is drained out from one side while fresh medium is added from the other.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, B and D only
Once a gene is cloned and expressed, the protein has to be made in bulk. A bioreactor gives the cells the best growth conditions, and one of these conditions is oxygen, not carbon dioxide.
A. If any protein encoding gene is expressed in a heterologous host, it is called a recombinant protein. — True. A heterologous host is a host of a different kind from the organism the gene came from. The protein it makes from the foreign gene is a recombinant protein.
B. Bioreactors are vessels in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial, plant, animal or human cells. — True. This is how the book describes a bioreactor.
C. A bioreactor provides optimum growth conditions such as temperature, pH, substrate, salts, vitamins and carbon dioxide for achieving the desired product. — False. The last item in the list is oxygen. The cells need oxygen, which is why a bioreactor has an oxygen delivery system and a stirrer for oxygen availability.
D. In a continuous culture system, the used medium is drained out from one side while fresh medium is added from the other. — True. This keeps the cells in their most active log/exponential phase, so the biomass and the yield of protein are higher.
NCERT Extract:
Obtaining the Foreign Gene Product – “… If any protein encoding gene is expressed in a heterologous host, it is called a recombinant protein. … The cells can also be multiplied in a continuous culture system wherein the used medium is drained out from one side while fresh medium is added from the other to maintain the cells in their physiologically most active log/exponential phase. … Thus, bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial plant, animal or human cells. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen).”