8.4.1Unit 6: Practical Skills in Biology II
Drug Production from Genetically Modified Organisms — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 5 parts Lesson 45 of 48 Unit quiz
Section 1 of 5Genetic Engineering Basics
Many medicines are proteins, and engineered organisms can make them in large amounts.
Genetic Engineering Basics
Genetic engineering
- A gene for a useful characteristic is taken from one organism and placed in another, where it is expressed as a protein.
Recombinant DNA
- DNA that combines nucleotide sequences from two different sources, often from different species, is called recombinant DNA.
GMO
- An organism that carries recombinant DNA, and therefore a transferred gene, is called a genetically modified organism.
Why it works
- The genetic code and the machinery of transcription and translation are universal, so a human gene can work inside a bacterium.
Medical aim
- Microorganisms, plants and animals can all be engineered to manufacture human proteins that are used as drugs or treatments.
Section 2 of 5Making a Drug in Bacteria
1
Restriction enzymes cut the required gene, such as the human insulin gene, out of the donor DNA at specific base sequences.
2
The polymerase chain reaction uses DNA polymerase to build many identical copies of the gene from free nucleotides.
3
DNA ligase joins each copy into a plasmid vector that has been cut with the same restriction enzyme, forming a recombinant plasmid.
4
The plasmids are taken up by bacteria, which are then grown in a fermenter with nutrients so that they multiply rapidly.
5
The bacteria express the gene, and the protein is separated, purified, packaged and distributed for medical use.
Section 3 of 5Making a Drug in Plants and Animals
Plant vector
- A gene is placed in a plasmid in bacteria, and the bacteria then infect plant cells and pass the gene into them.
Plant product
- The protein can be purified from the plant tissue, or the plant can be eaten so that the drug is delivered directly.
Animal method
- The gene is injected into the nucleus of a fertilised egg, which is placed in the uterus of a surrogate female.
Animal expression
- Every cell of the resulting animal carries the gene, so the protein can be collected, for example from its milk.
Examples
- Human insulin and clotting factors come from bacteria, a cholera vaccine from plants and clotting proteins from animal milk.
| Host | Gene delivered by | Where the product is collected |
|---|---|---|
| Bacterium | Plasmid vector | Fermenter culture |
| Plant | Bacterial infection of plant cells | Plant tissue or edible parts |
| Animal | Injection into a zygote | Milk of the adult animal |
Section 4 of 5Comparing the Hosts
Comparing the Hosts
Bacteria
- They divide quickly and are cheap to grow in fermenters, but they cannot always fold or modify complex proteins correctly.
Plants
- They can be grown on a large scale and may deliver an oral drug, but the process of modification is slow.
Animals
- They can process complex human proteins, but raising them is costly and raises welfare and ethical concerns.
Purity
- Whatever the host, the product must be isolated and purified so that it contains none of the host proteins or toxins.
Section 5 of 5Exam Checklist & Tips
8.4.1 – Key Points for the Exam
- Genetic engineering Deliberately transferring a gene from one organism into another so that a new characteristic is expressed.
- Recombinant DNA DNA made by combining nucleotide sequences from different sources, often different species.
- Vector A carrier, such as a plasmid, that transfers a gene into a host cell.
- Fermenter A large container where genetically modified microorganisms are grown to make a product.
- Genetically modified organism An organism that carries recombinant DNA and expresses the transferred gene.
Common Mistakes
- Saying that the gene is made by the bacterium;
- the gene is copied from the donor, and the bacterium makes the protein.
- Forgetting that the same restriction enzyme must cut both the gene and the plasmid so that the sticky ends match.
- Stating that PCR joins the gene to the plasmid;
- joining is done by DNA ligase, while PCR only copies the gene.
- Writing that the animal is injected with the protein; it is the gene that is injected into the zygote.
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