Recombinant DNA technology is an important tool in understanding the structure, function and regulation of genes and their products. It is a complex step-by-step process. The first few steps in DNA recombinant technology involve the isolation of the genetic material, fragmentation of DNA by restriction endonucleases and amplification of a gene of interest.
Once the foreign DNA has been extracted, the next steps are insertion of recombinant DNA into the host cell or organism, obtaining the foreign gene product and downstream processing. Techniques used to carry out the last three steps. Insertion of recombinant DNA into the host cell is one of the most challenging steps as first, the bacterial cell has to be made competent to receive the DNA. If we consider the insertion of a recombinant-DNA-bearing gene for ampicillin into the host cell E Coli, the host cells will become ampicillin-resistant. Thereafter, when the host cells are spread on agar plates containing ampicillin, only the transformants will grow. On the other hand, non-transformant recipient cells will die. In this case, the ampicillin resistance gene acts as a selectable marker since it identifies and eliminates non-transformants and permits the growth of transformants. If any protein-encoding gene is expressed in many hosts such as plant cells, bacterial cells and fungal cells, it is called a recombinant protein.
For example, the inoculation port is used to introduce initial inoculums and the nutrient port to introduce more nutrients. Similarly, the anti-foam port is used to introduce anti-foaming agents while the pH port to introduce acids or alkalis to maintain optimal pH. At the base of the tank, there is a harvest line to extract the culture medium and microbial products. Another type of bioreactor is the one with a sparged stirred tank. Sterile air bubbles are sparged through this reactor, which increases the surface area for oxygen transfer. Once the biomass has been obtained from the bioreactor, the final step in the recombinant DNA technology is downstream processing. It refers to the recovery and purification of biosynthetic products such as pharmaceuticals before they are brought to the market as finished products. In downstream processing, pharmaceutical products such as antibiotics and hormones are formulated with suitable preservatives. Thereafter, these products are also subjected to clinical trials and quality testing. By aiding in the development of these new medicines and vaccines, recombinant DNA technology has revolutionised medical science and opened new vistas of research.