13.1 - Genetic Engineering

Genetic Engineering and Genetically Modified Organisms (GMO)

Definition of Genetic Engineering

• Genetic engineering is a gene manipulation technique to modify an organism’s genetic material to produce new combinations of genes.
• It transfers a DNA segment from one organism to another by recombinant DNA technology.
• Recombinant DNA technology enables biologists to recombine the DNA or genome of an organism.
• A genome is a complete set of DNA that includes all the genes and information needed to build and carry out the life processes of an organism.

Genetically Modified Organisms (GMO)

• A genetically modified organism (GMO) is an animal, plant or microorganism produced by recombinant DNA technology.
• GMOs contain recombinant DNA; an organism that contains recombinant DNA is a transgenic organism.
• Recombinant DNA technology produces new gene combinations.
• Examples:
  • A genetically modified cow produces milk without β-lactoglobulin, a protein that causes allergy among some children.
  • A genetically modified goat possesses a human gene that codes for a blood clotting factor. The factor is obtained from its milk, purified and used to treat haemophilic patients.

Genetically Modified Food (GMF)

• Genetically modified food (GMF) possesses DNA from another plant or animal species.
• Recombinant DNA technology produces crops and livestock with beneficial characteristics.
• Examples include paddy, oil palm, pineapple, corn, soya bean, salmon, cattle and goat.
• GMF characteristics: resistance to pests, herbicides and diseases; application in medicine; and tolerance to heavy metals.
• Examples:
  • A Bacillus thuringiensis gene is inserted into corn to increase resistance to insect pests.
  • A growth hormone gene from Chinook salmon is inserted into the genome of Atlantic salmon. The resulting Super Salmon grows faster and can be produced throughout the year.
  • A gene from Arabidopsis sp. that enables tolerance to freezing conditions is inserted into the potato genome, producing potatoes that grow well in cold climates.

Advantages and Disadvantages of GMF

• Advantages:
  • Overcomes worldwide food shortage by producing high-quality transgenic crops and livestock.
  • Reduces food-production costs.
  • Increases the nutritional value of crops.
  • Reduces crop-pest problems and pesticide use.
  • Higher production lowers food prices and increases food availability.
• Disadvantages:
  • Endangers natural species.
  • A slight possibility exists that a foreign gene, such as an antibiotic-resistance gene, may be transferred to humans.
  • Human health and genetic material may be adversely affected.
  • Other health implications of GMF consumption are still unknown.

Insulin Production through Genetic Engineering

Steps of Insulin Production

• Insulin controls blood glucose level.
• Previously, insulin extracted from cattle or pig pancreases was used to treat diabetes mellitus patients.
• Insulin can now be produced commercially by genetic engineering using Escherichia coli.

1. The insulin gene is cut from a human DNA fragment using restriction enzymes.
2. A bacterial plasmid—circular DNA used as a cloning vector—is cut using restriction enzymes.
3. The human insulin gene is inserted into the plasmid and joined by DNA ligase, forming a recombinant plasmid.
4. The recombinant plasmid is introduced into a bacterium, producing a transgenic bacterium.
5. Bacterial clones multiply and produce insulin in their cells.
6. Insulin is extracted from the bacteria and purified.

Other Products of Genetic Engineering

• Hepatitis B vaccine
• Blood clotting factor
• Growth hormone