Biology · Biotechnology: Principles and Processes · NEET
NCERT defines it clearly: if any protein-encoding gene is expressed in a heterologous host (a host that is not its natural source), the protein made is called a recombinant protein. Example: human insulin gene put into bacteria makes recombinant human insulin. The word 'recombinant' here points to the gene's foreign origin, not the protein's shape.
Cloning only multiplies the DNA copies. But the final aim of almost all recombinant technologies is a useful protein, not more DNA. So the recombinant DNA must be expressed, meaning it must be transcribed and translated into protein under suitable induced conditions. Without expression you have plenty of the gene but zero product.
Small laboratory cultures give only tiny amounts of protein. NCERT states that small-volume cultures cannot yield appreciable quantities of product. Medicines and industrial enzymes are needed in large amounts, so cells must be multiplied on a large scale to get enough recombinant protein economically.
It is a growth method where used (spent) medium is drained out from one side while fresh medium is added from the other side. This keeps the cells in their most active log (exponential) phase for a long time. It produces a larger biomass, and therefore higher yields of the desired protein, than a small batch culture that stops when nutrients run out.
No, but they are directly linked. Obtaining the foreign gene product is the idea that you must express the gene and grow cells in large amounts. The bioreactor is the actual vessel used to do that large-scale growth (100 to 1000 litres). The bioreactor is the tool; obtaining the product is the goal it serves.
Expression of the foreign gene and growing the cells to make protein are upstream (biosynthetic) events. Separation and purification of that protein afterwards are downstream processing. NEET often traps students by listing 'expression' as a step of downstream processing, which is wrong.
Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes?
Which of the following statements is incorrect?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
NCERT says the ultimate aim of almost all recombinant technologies is to produce a desirable protein. So expressing the cloned gene to obtain the recombinant protein is the real goal, not just copying DNA.
A heterologous host is a host organism different from the natural source of the gene, for example bacteria carrying a human gene. A protein expressed in such a host is a recombinant protein.
Fresh medium is added while spent medium is removed, keeping cells in the active log phase continuously. This gives more biomass and therefore more recombinant protein than a batch culture that stops growing when nutrients finish.
Yes. NCERT notes cells with the cloned gene can first be grown on a small scale in the lab to extract and purify the protein. But for commercial amounts, large-scale culturing in bioreactors is needed.
After the protein is produced by expression and large-scale growth, it goes to downstream processing, which includes separation, purification, formulation with preservatives, and quality control before marketing.
