Inheritance and ecology · GCSE Biology
Genetic engineering
Explain genetic engineering for GCSE Biology: cut a gene with restriction enzymes, insert it into a plasmid with ligase, transform bacteria, and evaluate GM crops and insulin without hype or panic.
Same language as bacteria: plasmids. Cut the useful gene and the plasmid with the same restriction enzyme, join with ligase, put the plasmid into bacteria, culture them, harvest the protein (insulin). Plants: insert a gene for herbicide resistance or vitamin production.
The important bits
What you need to know
- 1
Genetic engineering is moving a gene from one organism to another so the host expresses a new protein. The organism is then genetically modified (GM).
- 2
Human insulin: the insulin gene is cut from human DNA using a restriction enzyme (leaves sticky ends). A bacterial plasmid is cut with the same enzyme. Ligase joins the gene into the plasmid. The plasmid is inserted into bacteria. The bacteria are grown in a fermenter and produce insulin, which is purified for Type 1 diabetes.
- 3
Advantages of GM insulin versus animal insulin: human protein (fewer immune reactions), large supply, no need to harvest pig or cow pancreases.
- 4
GM crops: genes for herbicide resistance, insect resistance (Bt toxin), or extra nutrients (golden rice with a vitamin A precursor). Benefits: yield, less pesticide, reduced deficiency disease. Concerns: wild gene flow, effects on non-target insects, corporate control of seed, unknown long-term ecology, food-labelling ethics.
- 5
Restriction enzymes cut DNA at specific sequences. Ligase is the joining enzyme. Vectors are usually plasmids (bacteria) or viruses in some research contexts.
- 6
This is not selective breeding. Selective breeding crosses whole organisms over generations; genetic engineering transfers one (or a few) named genes, even between kingdoms (human gene in a bacterium).
- 7
Cloning (tissue culture, embryo splitting, adult cell cloning / Dolly) is different again: it copies a whole genome, rather than adding one gene. Keep the three techniques separate.
- 8
Ethics: human insulin is widely accepted; GM food is more contested. Evaluation needs a biological benefit, a risk, and a conclusion, not a slogan.
Quotations worth analysing
Short evidence. Real method.
“Restriction enzymes cut DNA; ligase joins the gene into the plasmid.”
Same enzyme on gene and plasmid so sticky ends match. Missing ligase or calling the plasmid a nucleus loses marks.
“Bacteria with the recombinant plasmid produce human insulin.”
The protein is human; the factory is prokaryotic. Type 1 patients inject that insulin.
“Genetic engineering transfers genes; selective breeding crosses organisms.”
Speed and the ability to move genes across species are the engineering advantages. Selective breeding uses whole genomes and existing variation.
Go deeper
What is the insulin method as a numbered list I can recite?
1. Identify the human insulin gene. 2. Cut it out with a restriction enzyme, producing sticky ends. 3. Cut a bacterial plasmid with the same restriction enzyme. 4. Mix; complementary sticky ends pair. 5. Ligase seals the sugar–phosphate backbone (recombinant plasmid). 6. Insert the plasmid into bacteria (transformation), often using heat shock or electricity in outline. 7. Select bacteria that took up the plasmid (antibiotic-resistance gene on the plasmid is the usual marker). 8. Culture in a fermenter with nutrients and oxygen. 9. Harvest and purify insulin. That list is a six-to-nine mark if you keep the enzymes named. Do not grow the human in a tank. Do not put the plasmid into a human pancreas as the industrial method.
Go deeper
How do I evaluate GM crops without copying a newspaper?
Benefit: insect-resistant cotton can reduce insecticide sprays; herbicide-resistant soya can simplify weeding and raise yield; golden rice can supply beta-carotene where vitamin A deficiency causes blindness. Risk: the transgene might spread to wild relatives; Bt toxin might harm non-target insects; pests might be selected for resistance (natural selection again); farmers may depend on one company’s seed; some consumers want a choice via labelling. Conclusion: case by case — medical GM insulin is established; a crop needs field data on yield, ecology and gene flow. “GM is unnatural” is weak because crop plants are already products of thousands of years of selection. “GM will save the world” is also weak without a named gene and a named problem.
Go deeper
How is this different from cloning and from CRISPR headlines?
GCSE genetic engineering is gene transfer with restriction enzymes, ligase and plasmids (or Agrobacterium for plants, if mentioned). Cloning copies an individual: plant tissue culture from meristems, or adult cell cloning (nucleus into an egg, surrogate mother — Dolly). CRISPR is a newer editing tool; unless your specification names it, do not rely on it. If a question says “how is a GM bacterium made?”, use the plasmid list. If it says “how is a prize cow copied?”, that is cloning, not restriction enzymes. Mixing those techniques is the usual mid-grade muddle. Stick to the named enzymes and the insulin or crop example in the stem.
See the idea in action
Describe how bacteria are engineered to make insulin. The human insulin gene is cut with a restriction enzyme. A plasmid is cut with the same enzyme. Ligase inserts the gene into the plasmid. The plasmid is placed in bacteria, which are cultured; they produce insulin that is collected and used to treat Type 1 diabetes. This is genetic engineering, not selective breeding, because a single human gene is functioning in a prokaryotic cell. Evaluation of GM herbicide-resistant maize would need a yield or spray-reduction benefit and a gene-flow or ecology risk, then a judgement.
Exam technique
Turn knowledge into marks
Learn restriction enzyme, sticky ends, plasmid, ligase, transform bacteria, fermenter, insulin. Compare with selective breeding in one sentence. For GM crops, give a named benefit and a named risk. Do not confuse with cloning.
Common mistakes
Do not give these marks away
- 01
Forgetting ligase or using different restriction enzymes on gene and plasmid so the ends do not match.
- 02
Calling genetic engineering selective breeding, or describing Dolly when the question is insulin.
- 03
Evaluating GM food with only “it is not natural”, with no gene, crop or ecological mechanism.
Which enzymes are used to cut a gene and then join it into a plasmid?
AAmylase and lipase
BRestriction enzyme and ligase
CInsulin and glucagon
DADH and adrenaline
Show the answer
Restriction enzyme and ligase. Restriction enzymes cut DNA at specific sites; ligase joins the gene into the opened plasmid. Digestive enzymes and hormones are the wrong topics.
Quick questions
If this is the bit you searched
How is insulin made by genetic engineering?
The human insulin gene is cut with a restriction enzyme, inserted into a plasmid using ligase, and placed in bacteria. The bacteria produce insulin, which is purified.
What is a plasmid used for in genetic engineering?
It is a vector: a small ring of DNA that can carry a new gene into a bacterium so the cell makes the new protein.
What is the difference between genetic engineering and selective breeding?
Selective breeding crosses whole organisms over generations. Genetic engineering transfers a specific gene, even from a different species, in one procedure.
What are the risks of GM crops?
Gene flow to wild plants, effects on other insects, pest resistance evolving, and social issues around seed control and labelling. Benefits can include higher yield and less pesticide.