4.3.1Use of Biological Resources
The Process of Genetic Modification — Edexcel International GCSE Science Double Award (Modular) - Biology Unit 2 Revision Notes & Topical Questions
5 min read 6 parts Lesson 12 of 15
Part 1 of 4Genetic modification
Genetic modification
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes,
- which may come from another species.
- The organism is genetically modified (transgenic) and contains recombinant DNA.
Examples
.
- Human insulin made by bacteria.
- Insect-resistant crops (e.g. Bt maize, soya) containing a bacterial gene for an insect poison.
- Herbicide-resistant crops, so only weeds are killed.
- Vitamin-enriched crops, e.g. Golden Rice, whose grains make a chemical that is turned into vitamin A.
Part 2 of 4Making human insulin with bacteria (Supplement)
1
Identify the insulin gene and cut it from human DNA with a restriction enzyme, leaving sticky ends (short unpaired single-stranded sections).
2
Cut a bacterial plasmid with the same restriction enzyme, giving complementary sticky ends.
3
Mix the gene and the plasmid; the sticky ends pair by complementary base pairing (A–T, C–G).
4
DNA ligase joins the sugar-phosphate backbones to make a recombinant plasmid.
5
Insert the recombinant plasmid into a bacterium (the plasmid is the vector).
6
Grow the bacteria in a fermenter; they multiply by binary fission and copy the plasmid each time.
7
The bacteria transcribe and translate the gene, making human insulin.
8
Extract and purify the insulin.
Roles
- Roles a restriction enzyme cuts DNA; DNA ligase joins it.
Why bacteria
- Why bacteria the universal genetic code means the human gene makes identical human insulin, avoiding the allergic reactions and supply limits of insulin from animals.
Part 3 of 4GM crops: advantages and disadvantages
| Advantages | Disadvantages and concerns |
|---|---|
| Insect-resistant crops lose less to pests and need less insecticide | GM seed costs more, and farmers may need to buy new seed each year |
| Herbicide-resistant crops allow weeds to be killed without harming the crop, giving higher yields | Genes may spread to wild relatives by pollen, producing herbicide-resistant weeds |
| Vitamin-enriched crops reduce deficiency disease | Reduced biodiversity and genetic variation, e.g. in monocultures or where herbicide use removes wild plants |
| Higher yields help feed a growing population; less spraying is cheaper and better for the environment | Harm to non-target insects, dependence on the same companies' chemicals, ethical objections and possible (unproven) health effects |
Part 4 of 4More from the specification
1Industrial Applications of Microorganisms
- Microorganisms such as yeast and fungi are cultivated in large-scale fermenters under regulated temperature, pH,
- and oxygen levels to mass-produce valuable commercial biological molecules.
2Anaerobic Bioethanol Production by Yeast
- Yeast cells metabolise plant sugars anaerobically to yield ethanol and carbon dioxide, serving as a renewable biofuel alternative to petroleum.
3Pectinase in Fruit Juice Clarification
- Commercial fungal enzymes (pectinases) break down insoluble pectin in plant cell walls, extracting a higher volume of clear fruit juice.
4Lactase in Lactose-Free Milk Production
- Immobilised lactase enzymes hydrolyse milk disaccharide lactose into absorbable monosaccharides for lactose-intolerant consumers.
- (glucose and galactose)
5Protein
- A long chain of amino acids containing carbon, hydrogen, oxygen and nitrogen.
6Optimum
- The temperature or pH at which activity is highest.
7Microorganism
- A living organism so small that it can only be seen clearly with a microscope.
8Lactose
- A disaccharide of glucose and galactose.
9Fungus
- An organism with a body of hyphae that feeds on organic matter, some of which cause disease.
10Respiration
- Chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
11Ethanol
- Alcohol produced by yeast in anaerobic respiration.
12Penicillin
- An antibiotic that inhibits bacterial cell wall synthesis.
Key terms
| Term | Meaning |
|---|---|
| Genetic modification | Changing the genetic material of an organism by removing, changing or inserting individual genes. |
| Plasmid | A small circular loop of DNA in bacteria, used as a vector to carry a gene. |
| Restriction enzyme | An enzyme that cuts DNA at a specific base sequence, leaving sticky ends. |
| Sticky ends | Short single-stranded ends left after cutting that pair with complementary ends. |
| DNA ligase | An enzyme that joins pieces of DNA together. |
| Recombinant plasmid | A plasmid containing a gene inserted from another organism. |
Avoid these mistakes
Avoid these mistakes
DNA ligase cuts the plasmid — a restriction enzyme cuts; DNA ligase joins.
GM crops have no drawbacks — cost, gene spread and reduced biodiversity are concerns.
Last updated: