A small piece of circular DNA called a plasmid? is extracted from the bacteria or yeast cell.
A small section is then cut out of the circular plasmid by restriction enzymes, ‘molecular scissors’.
The gene for human insulin is inserted into the gap in the plasmid. This plasmid is now genetically modified.
The genetically modified plasmid is introduced into a new bacteria or yeast cell.
This cell then divides rapidly and starts making insulin.
To create large amounts of the cells, the genetically modified bacteria or yeast are grown in large fermentation vessels that contain all the nutrients they need. The more the cells divide, the more insulin is produced.
When fermentation is complete, the mixture is filtered to release the insulin.
The insulin is then purified and packaged into bottles and insulin pens for distribution to patients with diabetes.