# 136 Genetic engineering, putting human insulin genes into bacteria

Genetic engineering is a process of taking a gene from one species and putting it into another species.

The control of all the normal activities of a bacterium depends upon its single chromosome and small rings of genes called plasmids. In genetic engineering pieces of chromosome from a different organism can be inserted into a plasmid. This allows the bacteria to make a new substance.

Using genetic engineering to put human insulin genes into bacteria

Credit: BBC Bitesize

1. Human cells with genes for healthy insulin are selected.
2. A chromosome (a length of DNA) is removed from the cell.
3. The insulin gene is cut from the chromosome using restriction endonuclease enzyme.
4. A suitable bacterial cell is selected. Some of its DNA is in the form of circular plasmids.
5. All the plasmids are removed from the bacterial cell.
6. The plasmids are cut open using the same restriction endonuclease enzyme.
7. The human insulin gene is inserted into the plasmids using ligase enzyme.
8. The plasmid are returned to the bacterial cell (only one is shone in the diagram).
9. The bacterial cell is allowed to reproduce in a fermenter. All the cells produced contain plasmids with the human insulin gene. 

Using genetic engineering to produce bacteria that make human insulin.

The importance of this process 

• Diabetics need a source of insulin to control their blood sugar level. In the past cow insulin has been used, but some people are allergic to it. Human insulin produced from genetically engineered bacteria will not trigger an allergic reaction. 
• The insulin is acceptable to people with a range of religious belief who may not be allowed to use insulin form animals such as cows or pigs.
• The product is very pure.
• Human insulin can be made on a commercial scale, reducing costs.

Video Genetic Engineering

Video Genetically Engineered Insulin