Expression of the Gene to Obtain the Desired Product

The final step in the six-step methodology of rDNA technology is expression of the cloned gene, and it follows directly from the previous step: once the transformed host cells have been selected and allowed to multiply in fresh culture medium, a large population of cells carrying the recombinant DNA is available. At this stage the cloned gene is switched on so that the host cell's own transcription and translation machinery reads it and manufactures the desired product -- this could be an alcohol, an enzyme, an antibiotic, or any number of other useful biological products. Because commercial-scale quantities of the product are usually needed, this expression step is carried out on a large scale inside a bioreactor, a vessel that maintains the conditions the transformed cells need to grow and synthesise the product efficiently a …