Genetic engineering
Genetic engineering means transferring a gene from one organism into another so that the recipient organism shows a useful new characteristic. Unlike selective breeding, which reshuffles existing alleles, genetic engineering can move genes between species.
The basic process (you must be able to outline this)
- Cut out the desired gene from the DNA of the donor organism using restriction enzymes, which cut DNA at specific sequences (HT).
- Insert the gene into a vector — usually a bacterial plasmid or a virus. The vector is also cut by the same restriction enzymes so the ends match. Ligase enzymes seal the gene into the plasmid (HT).
- Transfer the vector into the cells of the target organism — often when the organism is at an early stage (an embryo or a young plant).
- The cells divide and grow carrying the new gene, which is then transcribed and translated to make the new protein.
✦Worked example— Examples (learn at least three)
Bacteria producing human insulin. The gene for human insulin is inserted into bacteria (E. coli). Bacteria multiply rapidly in fermenters and produce human insulin which is purified and used to treat type-1 diabetes. Before genetic engineering, insulin had to be extracted from the pancreases of cattle and pigs (different structure, sometimes caused reactions).
GM crops.
- Disease/pest resistance — bt-toxin gene from a soil bacterium added to maize/cotton makes the crop's own tissues toxic to caterpillars.
- Herbicide resistance — crops survive being sprayed with broad-spectrum weed killers, allowing easier weed control.
- Increased yield / size of grain.
Golden rice. Rice modified to produce beta-carotene (a precursor of vitamin A). Could prevent vitamin A deficiency, a leading cause of childhood blindness in parts of South-East Asia.
Sheep producing pharmaceuticals in their milk (e.g. blood-clotting factor for haemophilia).
Gene therapy (extension)
Some inherited diseases (cystic fibrosis, certain immune disorders) are being treated experimentally by inserting a healthy copy of the gene into a patient's own cells, often using a viral vector. Currently complex and expensive but a major area of research.
Benefits
- Disease-resistant and higher-yielding crops can address food security.
- Pure human protein (e.g. insulin) avoids allergic reactions.
- Plants that produce vitamins (golden rice) can save lives.
- Gene therapy may one day cure inherited diseases.
Concerns
- Effects on wild populations. GM genes may spread into wild relatives.
- Long-term safety. Effects on people and ecosystems may take decades to appear.
- Insect populations. Insects that feed on GM crops may evolve resistance, or non-target insects may be harmed.
- Cost and ownership. GM seeds are sold by large companies; farmers cannot always save seed.
- Ethics. Some people object to "playing God" with the genome, particularly in animals or humans.
How is GM regulated?
In the UK and EU, GM crops require approval from regulators based on safety and environmental impact. There are tighter restrictions on growing GM food than on importing it.
⚠Common mistakes
- Confusing genetic engineering with selective breeding. SB shuffles existing alleles within a species; GE moves genes between species.
- Saying GM = Frankenfood. The actual changes are usually small, but the principles behind concerns are real.
- Thinking insulin still comes from animals. Almost all human insulin today is made by GM bacteria.
- Forgetting the role of plasmids and enzymes. Restriction enzymes cut, ligase joins, plasmids carry.
Links
Built on B6.2 and B6.3 (DNA, transcription/translation). Compare with B6.6 (selective breeding) and B6.8 (cloning, often used to copy a successful GM organism).
AI-generated · claude-opus-4-7 · v3-deep-biology