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Genetic engineering

Genetic engineering involves changing the DNA of an organism, usually by deleting, inserting or editing a gene to produce desired characteristics.

Fermentation

Process where microorganisms are cultured so that they reproduce and increase in quantity.

Organelles

A distinct part of the cell, such as the nucleus, ribosome or mitochondrion, which has structure and function.

Microbes

Microorganisms such as bacteria, yeasts and fungi

Cytosine (C)

The nitrogenous base, cytosine, which pairs with G, guanine.

Thymine (T)

The nitrogenous base, thymine, which pairs with A, adenine.

Guanine (G)

The nitrogenous base, guanine, which pairs with C, cytosine.

Adenine (A)

The nitrogenous base, adenine, which pairs with T, thymine.

Sterile

Uncontaminated by microorganisms

Bases

Bases, sometimes called nitrogenous bases, are the parts of the DNA molecule that join the two helix strands. They are like rungs on a ladder. There are four bases: adenine (A), thymine (T), guanine (G) and cytosine (C). Each base can only join with one other base; i.e. they join together in pairs: A with T and G with C.

Making human insulin

For many years, insulin was obtained by purifying it from the pancreas of cows and pigs slaughtered for food. This was expensive and time consuming.

Insulin is now made by genetically-engineered microbes. This enables human insulin to be produced in large quantities and then purified.

Insulin gene

The amino acid sequence of insulin was found in 1955. Knowing this sequence, and understanding the triplet code for the bases on DNA, has allowed researchers to synthesise the gene for human insulin. This could then be used to genetically modify bacteria to produce human insulin.

Use the information in the table to produce the DNA base sequence for the first three amino acids of the insulin A-chain.

Genetic code

A sequence of three DNA bases (triplet) code for one amino acid.

amino acid 1st base 2nd base 3rd base
valine G T T
isoleucine A T T
glycine G G C
Quiz 1 Print

Genetic engineering to make human insulin

The animation shows an overview of how genetic engineering can be used to produce human insulin. The enzymes involved are shown in the lower animation.

Details of the enzymes involved.

Producing human insulin

Human insulin is produced in a very controlled and sterile environment.

Genetically-engineered bacteria are grown in large stainless steel fermentation vessels. The vessel contains all the nutrients needed for growth.

When the fermentation is complete, the mixture containing the bacteria is removed from the fermentation vessel. The bacteria are filtered off and broken open to release the insulin they have produced. The insulin is separated from all the other proteins and organelles from inside the bacteria and once purified it is packaged for distribution.

All the equipment is kept sterile to prevent contamination and regular checks make sure that the insulin meets the required quality standards.

Fermentation vessel in a factory

Fermentation vessel in a factory

Production and packaging of insulin pens

Production and packaging of insulin pens

Insulin pens

Insulin pens

Images courtesy of Novo Nordisk

Question 6