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The stages of this method of genetic engineering are:

• The location of the section of DNA containing the gene for making the human protein insulin must be identified (it is on human chromosome number 7).
• A specific enzyme is used to extract the required gene from the human chromosome.
• Plasmids are then removed from bacterial cells.
• The DNA of the plasmids is cut open with a specific enzyme.
• The human insulin gene is inserted into each plasmid.
• The plasmid acts as a vector - it is used to transfer DNA from one organism to another.
• Bacterial cells are made to take up the genetically modified plasmids.
• Bacterial cells that successfully take up plasmids are described as being transformed. They can also be called genetically modified organisms. The bacteria are host cells for the plasmids.
• Each bacterial cell will produce a tiny mass of insulin.
• By culturing the genetically modified bacteria large quantities of insulin protein can be produced and extracted.