Why genetically engineered insulin is needed
People with Type 1 diabetes cannot produce sufficient insulin because their pancreatic beta cells are destroyed by the immune system. They need regular injections of insulin to control their blood glucose levels.
Previously, insulin was extracted from pig or cow pancreases, but this caused allergic reactions in some patients and required large numbers of animals. Genetically engineered human insulin is identical to the insulin produced by the human body, causes fewer side effects, and can be produced in unlimited quantities.
The step-by-step process
1. The human insulin gene is identified and cut from human DNA using a restriction enzyme. The restriction enzyme cuts at specific base sequences, producing fragments with "sticky ends".
2. A bacterial plasmid is cut open using the same restriction enzyme, producing matching sticky ends.
3. The human insulin gene is inserted into the open plasmid. The enzyme ligase joins the DNA fragments together, creating a recombinant plasmid.
4. The recombinant plasmid is inserted into a bacterium (e.g. E. Coli). The bacterium now contains the human insulin gene.
5. The genetically modified bacteria are grown in large fermenters under controlled conditions. As they reproduce, all daughter cells contain the insulin gene.
6. The bacteria produce human insulin, which is extracted, purified and packaged for medical use.
Key enzymes in the process
| Enzyme | Role |
|---|---|
| Restriction enzyme | Cuts DNA at specific base sequences, removing the insulin gene and opening the plasmid |
| Ligase | Joins the insulin gene into the plasmid by bonding the sugar-phosphate backbones together |
Using the same restriction enzyme to cut both the human DNA and the plasmid ensures that the sticky ends are complementary, allowing the gene to be inserted correctly. This is a critical detail that examiners frequently test.
Advantages of genetically engineered insulin
Identical to human insulin: Fewer allergic reactions compared to animal insulin. Unlimited supply: Bacteria reproduce rapidly in fermenters, so production is not limited by animal supply. No animals harmed: No need to slaughter pigs or cows for their pancreases. Consistent quality: The product is always the same, unlike animal-derived insulin which can vary.
Lower cost over time: Although setting up the process is expensive, the ongoing production cost per unit is lower than extracting insulin from animal sources. Acceptable to more patients: People with religious or ethical objections to animal products can use it.