Biotechnology and genetic modification
Why Bacteria are Ideal for Biotechnology
Biotechnology involves using living organisms to produce useful products. Bacteria are the most commonly used organisms in genetic modification (GM) for several fundamental biological and practical reasons. Understanding these reasons is key to answering both multiple-choice and theory questions.
The utility of bacteria stems from their rapid reproduction rate, their ability to synthesize complex molecules (proteins), and the specific biological structures they possess, such as plasmids. Additionally, their status as prokaryotes significantly reduces the ethical complexity compared to using higher animals.
Plasmid
A plasmid is a small, circular piece of DNA found in the cytoplasm of bacteria, separate from the main bacterial chromosome. Plasmids often carry genes that provide advantages, such as antibiotic resistance, but in biotechnology, they are used as vectors to carry foreign genes (e.g., the human insulin gene) into the bacterial cell.
Biotechnology / Genetic Modification
Genetic modification is the process of altering the genome (DNA) of an organism by inserting a gene from another species. Biotechnology is the broader application of this technology to produce goods, such as medicines or crops.
The Role of Plasmids in Genetic Modification
To modify a bacterium, scientists must insert a new gene into it. The plasmid is the vehicle for this insertion because:
| Feature | Explanation |
|---|---|
| Circular DNA | It is stable and can replicate independently of the bacterial chromosome. |
| Cutting Sites | Plasmids have specific restriction enzyme sites that allow scientists to cut them open and insert a foreign gene. |
| Marker Genes | Many plasmids contain marker genes (e.g., for antibiotic resistance) that allow scientists to identify which bacteria have successfully taken up the modified plasmid. |
Without plasmids, there would be no convenient, natural mechanism to introduce and maintain foreign DNA within the bacterial cell during replication.
Ethical Considerations: Bacteria vs. Animals
A critical advantage of using bacteria in biotechnology is the few ethical concerns associated with their manipulation and growth compared to using mammals or other sentient animals.
Why are there few ethical concerns?
| Aspect | Explanation |
|---|---|
| Sentience | Bacteria are prokaryotes. They lack a nervous system, brain, and central nervous system. Therefore, they cannot feel pain or suffering. This removes the primary ethical objection to using animals in research (animal welfare). |
| Growth Context | Bacteria are grown in large-scale fermenters (bioreactors) under controlled conditions. This industrial process does not involve the rearing, transport, or slaughter of livestock, which are major sources of ethical debate in animal-based biotechnology. |
| Scope of 'Few' | Note that there are safety concerns (e.g., preventing escape into the environment), but these are technical/biosecurity issues, not ethical issues regarding the welfare of the organism itself. The syllabus specifically asks about ethical concerns. |
This contrasts sharply with using animals (e.g., sheep or goats) to produce pharmaceuticals in their milk, where significant ethical debates regarding animal welfare and genetic integrity exist.
Worked Example: Rapid Reproduction
Question: Explain why the rapid reproduction rate of bacteria makes them useful in biotechnology. [2 marks]
Answer:
- Bacteria reproduce rapidly (e.g., by binary fission every 20 minutes). [1 mark]
- This allows for the quick production of large quantities of the desired product (e.g., insulin) in a short time. [1 mark]
Reasoning: The examiner looks for the link between speed and quantity. Simply stating 'they grow fast' is insufficient; you must explain the consequence: mass production of the molecule.
⚠︎ Confusing Ethical Concerns with Safety Concerns
Mistake: Students often write that bacteria have 'no ethical concerns' or confuse this with 'no safety risks'.
Correction:
- Use the phrase 'few' ethical concerns, not 'none', as there are always potential environmental risks (biosecurity).
- Do not mention 'pollution' or 'escape' as an ethical issue in this specific context. Ethical issues relate to welfare and sentience. Safety issues relate to environmental containment.
- Specifically state that bacteria lack a nervous system or cannot feel pain, which is the core reason for the reduced ethical burden.
Addressing 'Discuss' Questions on Ethics
When to use: When asked to discuss why bacteria are useful, specifically regarding ethical aspects.
Why examiners accept this: Examiners look for the distinction between sentience and non-sentience. They want to see that you understand that ethical concerns in biotechnology often revolve around animal welfare. Since bacteria are prokaryotes without a central nervous system, they do not experience suffering.
Correct Phrasing: 'Bacteria have few ethical concerns because they are prokaryotes and lack a nervous system, so they cannot feel pain or distress. This contrasts with using mammals, which raises animal welfare issues.'
Key Markscheme Keywords: few/no ethical concerns, no nervous system, cannot feel pain/suffering, prokaryote.
Past Paper Style Questions
Q:
State two reasons why bacteria are useful in biotechnology. [2]
A:
- Rapid reproduction rate.
- Ability to make complex molecules (or presence of plasmids).
Q:
Discuss why there are few ethical concerns over the use of bacteria in genetic modification compared to animals. [2]
A:
- Bacteria are prokaryotes / lack a nervous system.
- Therefore, they cannot feel pain or suffer (unlike sentient animals).
Q:
Identify the bacterial structure used to carry foreign genes in genetic modification. [1]
A:
Plasmid.