Genetic ModificationEdexcel GCSE Biology: Revision notes
Section 1
Selective Breeding
Humans choose organisms with desired traits and breed them over generations. Impact: higher yield/milk, disease resistance, docile animals.
Not the same as natural selection — humans choose, not the environment.
Section 2
Tissue Culture
Small groups of cells grown in a nutrient/hormone medium under sterile conditions to produce clones. Advantages: rapid, disease-free, year-round production, useful for research.
Section 3
Genetic Engineering: The Process
- Restriction enzymes cut out the gene, leaving sticky ends
- A vector (plasmid/virus) is cut with the same enzyme
- Gene inserted into vector; ligase joins sticky ends
- Vector transfers gene into target organism
Use all four terms in order for full marks.
Section 4
GM Crops
Bt gene from Bacillus thuringiensis gives crops insect resistance.
Advantages: higher yield, pest/disease resistance. Disadvantages: gene spread to wild plants, biodiversity loss.
Section 5
Fertilisers and Biological Control
Fertilisers add nutrients, boosting yield but risking eutrophication. Biological control uses natural predators, sustainable but can introduce new pest problems.
Biological control uses a whole organism, not DNA modification.
Section 6
Evaluating Benefits and Risks
Medicine: GM bacteria produce insulin. Ethical concerns: 'playing God', consent, animal welfare in breeding. Always weigh both sides plus a conclusion.
Evaluate questions need both sides and a judgement.
Must Know
- Selective breeding: humans choose parents over generations.
- Tissue culture: clones from tissue in sterile medium.
- Genetic engineering: restriction enzymes → sticky ends → vector → ligase.
- Bt gene gives insect resistance.
- Fertilisers risk eutrophication; biological control risks new pests.
That's the notes covered.
Carry on to the next subtopic.