Step 1: The insulin gene is a protein consisting of two separate chains of amino acids, an A above a B chain, that are held together with bonds. Both insulin genes is extracted from stem cells of healthy human pancreas using restriction enzymes.

Step 2: Using same restriction enzymes, plasmids are cut open for the insulin genes to attach to.
Step 3: These two insulin genes are then inserted into plasmids, small circular pieces of DNA that are more readily taken up by the host's DNA. This is called recombinant plasmids. The insulin and plasmid are sealed up using a special enzymes called ligase
Step 4: The recombinant plasmids are inserted into a non-harmful type of the bacterium of E. coli using a process called transfection.
Step 5: The bacteria synthesizing the insulin then undergo a fermentation process. They are grown at optimal temperatures in large tanks in manufacturing plants.
Step 6: After growing, the cells are taken out of the tanks and broken open to extract the insulin genes using multiple chemicals.

First, add a mixture of lysozome that digest the outer layer of the cell wall, second adding a detergent mixture that separates the fatty cell wall membrane. Third, adding cyanogen bromide, a reagent that splits insulin chains from the plasmid chains

Step 7: The two insulin gene chains are then mixed together and joined by disulfide bonds through the reduction-oxidation reaction. An oxidizing agent (a material that causes oxidization or the transfer of an electron) is added.