CIE iGCSE Biology-21.3 Genetic modification- Study Notes- New Syllabus
CIE iGCSE Biology-21.3 Genetic modification- Study Notes – New syllabus
CIE iGCSE Biology-21.3 Genetic modification- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- Describe genetic modification as changing the genetic material of an organism by removing, changing or inserting individual genes
- Outline examples of genetic modification:
(a) the insertion of human genes into bacteria to produce human proteins
(b) the insertion of genes into crop plants to confer resistance to herbicides
(c) the insertion of genes into crop plants to confer resistance to insect pests
(d) the insertion of genes into crop plants to improve nutritional qualities
Supplement
- Outline the process of genetic modification using bacterial production of a human protein as an example, limited to:
(a) isolation of the DNA making up a human gene using restriction enzymes, forming sticky ends
(b) cutting of bacterial plasmid DNA with the same restriction enzymes, forming complementary sticky ends
(c) insertion of human DNA into bacterial plasmid DNA using DNA ligase to form a recombinant plasmid
(d) insertion of recombinant plasmids into bacteria (specific details are not required)
(e) multiplication of bacteria containing recombinant plasmids
(f) expression in bacteria of the human gene to make the human protein - Discuss the advantages and disadvantages of genetically modifying crops, including soya, maize and rice
What Is Genetic Modification?
✅ Definition:
Genetic modification (also called genetic engineering) is the process of changing the genetic material of an organism by:
- Removing a gene
- Changing a gene
- Inserting a gene from another organism
🔍 Why Is It Done?
- To give the organism new traits (e.g., disease resistance, faster growth, or the ability to produce useful substances like insulin)
- To improve outcomes in farming, medicine, or industry
🧠 In Summary: Genetic modification means altering an organism’s DNA by adding, deleting, or changing specific genes to produce desired characteristics.
Examples of Genetic Modification (GM)
(a) Inserting Human Genes into Bacteria to Produce Human Proteins
- Purpose: To make useful medical proteins like insulin for diabetes treatment.
- How: The human insulin gene is inserted into bacterial plasmids. The bacteria reproduce and produce insulin, which is collected and purified.
📌 This is cheaper and more ethical than using animal insulin.
(b) Inserting Genes into Crop Plants to Confer Resistance to Herbicides
- Purpose: To allow crops to survive herbicide spraying.
- Example: GM soybeans with a gene for herbicide resistance allow weeds to be killed without harming the crop.
📌 Increases yield and reduces the need for manual weeding.
(c) Inserting Genes into Crop Plants to Confer Resistance to Insect Pests
- Purpose: To protect crops from insect pests naturally.
- Example: Bt crops (like Bt corn) contain a gene from Bacillus thuringiensis that produces an insect-killing toxin.
📌 Reduces pesticide use and prevents crop damage.
(d) Inserting Genes into Crop Plants to Improve Nutritional Qualities
- Purpose: To combat malnutrition by boosting food nutrients.
- Example: Golden Rice is genetically modified to produce beta-carotene (a source of vitamin A).
📌 Helps prevent vitamin A deficiency, especially in developing countries.
🧠 In Summary:
| Example | Benefit |
|---|---|
| Human gene → Bacteria | Produces medicines like insulin |
| Herbicide-resistance gene → Crops | Allows chemical weed control |
| Insect-resistance gene → Crops (Bt crops) | Reduces pest damage and pesticide use |
| Nutritional gene (e.g., Golden Rice) | Improves food value and prevents disease |
Genetic Modification: Bacterial Production of a Human Protein
Example: Producing human insulin using genetically modified bacteria.
(a) Isolation of the Human Gene
- The DNA carrying the human insulin gene is cut using restriction enzymes, which create “sticky ends”-short, single-stranded DNA sections ready to bind with matching DNA.
(b) Cutting the Bacterial Plasmid
- A bacterial plasmid (circular DNA) is cut open using the same restriction enzyme, creating complementary sticky ends that match the human gene.
(c) Inserting the Human Gene
- The human gene is inserted into the plasmid. DNA ligase joins the sticky ends, forming a recombinant plasmid (contains human DNA).
(d) Inserting the Plasmid into Bacteria
- The recombinant plasmid is introduced into bacterial cells. Now the bacteria carry the human gene within their plasmid.
- Specific transformation methods (like heat shock or electroporation) are not required at this level.
(e) Multiplying the Bacteria
- The genetically modified bacteria are placed in a fermenter. They reproduce rapidly, passing on the recombinant plasmid to each new cell.
(f) Producing the Human Protein
- As the bacteria grow, they read the inserted human gene and produce human insulin (or another desired protein). The product is extracted and purified for medical use.
🧠 In Summary – Step-by-Step Flow:
| Step | What Happens |
|---|---|
| (a) | Human gene cut out with restriction enzyme |
| (b) | Bacterial plasmid cut with same enzyme |
| (c) | Human gene inserted into plasmid using ligase |
| (d) | Recombinant plasmid inserted into bacteria |
| (e) | Bacteria multiply and copy recombinant plasmid |
| (f) | Bacteria express gene and make human protein |
Genetically Modified (GM) Crops: Advantages & Disadvantages
🌿 Advantages of Genetically Modifying Crops
| Advantage | Explanation |
|---|---|
| Increased resistance to pests | GM crops like Bt maize produce natural insect toxins, reducing need for pesticides. |
| Tolerance to drought or harsh conditions | Some GM crops are engineered to grow in dry or nutrient-poor soils (e.g., drought-resistant rice). |
| Improved nutritional value | Golden rice is genetically modified to contain vitamin A (beta-carotene), helping reduce deficiency in poor regions. |
| Herbicide resistance | GM soya can survive herbicide sprays, making weed control easier and more efficient. |
| Higher yield and longer shelf life | Leads to more food production and reduced waste. Beneficial in feeding growing populations. |
| Scientific and industrial use | GM crops can be used to produce medicines, vaccines, or biodegradable plastics. |
⚠️ Disadvantages of Genetically Modifying Crops
| Disadvantage | Explanation |
|---|---|
| Possible unknown health effects | Some fear that eating GM foods may cause allergies or long-term health problems (though no strong evidence exists). |
| Cross-contamination with wild plants | Pollen from GM crops might spread and affect non-GM or wild plant species. |
| Impact on small-scale farmers | GM seeds are often patented, which may make poor farmers dependent on large companies for buying seeds each year. |
| Harm to non-target species | Insect-resistant crops might also affect useful insects, like pollinators or natural pest predators. |
| Ethical and religious concerns | Some people object to tampering with nature or mixing genes between species. |
| Resistance development | Pests or weeds may adapt over time, making the GM protection less effective. |
🧠 In Summary: Genetically modified crops like soya, maize, and rice can bring huge benefits in farming, nutrition, and sustainability — but they also raise ethical, environmental, and economic concerns that need careful consideration.