1.5Unit 1 — Cell Biology
Genetic Engineering — SQA National 5 Biology — SQA National 5 Biology Revision Notes & Topical Questions
5 min read 2 parts Lesson 5 of 6
Section 1 of 2Stages of genetic engineering
- Stage 1: Identification & Extraction — The required gene is identified on a source chromosome (e.g. human chromosome containing the insulin gene) and extracted using a specific restriction endonuclease enzyme.
- Stage 2: Plasmid Extraction & Opening — A circular plasmid vector is extracted from a bacterial host cell and cut open using the same restriction enzyme, ensuring compatible sticky ends.
- Stage 3: Insertion & Sealing — The human gene is inserted into the cut open plasmid and permanently sealed into place using the enzyme DNA ligase to produce a recombinant plasmid.
- Stage 4: Transformation — The recombinant plasmid is inserted into a host bacterial cell, creating a genetically modified (GM) bacterium.
- Stage 5: Fermentation & Purification — The GM bacteria are cultured in large industrial fermenters under optimum growth conditions.
- As they multiply rapidly, they express the introduced gene,
- producing large quantities of the desired therapeutic protein,
- (e.g. human insulin or human growth hormone)
- which is then extracted and purified.
Section 2 of 2Applications and advantages
1Medical products produced by GM bacteria3 points
:
- Human insulinfor treating diabetes mellitus (eliminates allergic reactions associated with older animal-derived insulin).
- Human growth hormone (HGH)for treating pituitary dwarfism in children.
- Factor VIIIhuman blood clotting protein for treating haemophilia patients.
2Advantages of using microorganisms2 points
:
- Bacteria reproduce extremely rapidly under controlled conditions in fermenters.
- Large volumes of identical, pure human proteins are produced at lower cost with zero risk of animal virus transmission.
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