How are recombinant proteins made?

There are 6 basic steps for making recombinant proteins. 

1. Amplification of the gene of interest. This is done through PCR, in which the amplification of the gene of interest is carried out with 2 sets of primers and enzyme Taq polymerase. 
2. Insertion into the cloning vector. The insertion is carried out by using restriction enzymes that cut and paste DNA and subsequently produce a molecule of recombinant DNA; this process is known as transfection. 
3. Transformation into a protein expressing host, such as bacteria, yeast, or mammalian cells. 
4. Cells are harvested by centrifugation, and tests for identification of recombinant protein are carried out by using Western blot or fluorescence. 
5. Large-scale production of these proteins, by using prokaryotic and eukaryotic expression host systems. 
6. Isolation and purification of these recombinant proteins. Harvested cells are lysed to release cellular components such as recombinant DNA, and then purified to remove any remaining impurities.