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Students will be able to: <br>- explain that genes may be transferred between cells. Reference should be made to the transfer of <br>genes between organisms of the same species or different species u2013 transgenic plants or animals <br>- briefly explain how a gene that controls the production of human insulin can be inserted into <br>bacterial DNA to produce human insulin in medical biotechnology <br>- discuss the social and ethical implications of genetic engineering, with reference to a named <br>example
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Genetic Engineering Definition: a technique used to transfer genes from one organism to another
Lesson Objectives (f) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same or different species – transgenic plants or animals (g) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology (h) outline the process of large-scale production of insulin using fermenters (not in new syllabus) (i) discuss the social and ethical implications of genetic engineering, with reference to a named example Use the knowledge gained in this section in new situations or to solve related problems.
How does genetic engineering work? • Individual genes cut off from cells of one organism and inserted into the cells of another organism of the same/ different species using vectors • Plasmid: circular DNA from bacteria used to transfer genes; is an example of a vector • The transferred gene can express itself in the genetically engineered organism
Restriction enzymes • enzyme that cuts double- stranded DNA • enzyme makes two incisions, one through each of the phosphate backbones of the double helix without damaging the bases • The chemical bonds that the enzymes cleave can be reformed by other enzymes known as ligases, so that restriction fragments carved from different chromosomes or genes can be spliced together, provided their ends are complementary
Diabetes mellitus Body unable to control its blood glucose conc. within safe limits Kidney unable to reabsorb all the glucose Glucose not reabsorbed is excreted in the urine 2 main types: 1. Type 1 2. Type 2 ▪ ▪ ▪
Type 1 diabetes ▪ Juvenile/early-onset diabetes (occurs early in life) ▪ Due to inability of pancreas to produce sufficient insulin
Transferring the human insulin gene into bacteria 1. Obtain the human chromosome containing the insulin gene. 2. Cut the gene using a restriction enzyme to produce ‘sticky ends’ (a single strand sequence of DNA bases). These bases can pair with complementary bases to form a double strand 3. Obtain a plasmid from a bacterium. 4. Cut the plasmid with the same restriction enzyme. This produces complementary sticky ends 5. Mix the plasmid with the DNA fragment containing the insulin gene. 6. Add DNA ligase to join the insulin gene to the plasmid 7. Mix the plasmid with E.coli bacteria. 8. Apply temporary heat or electric shock. This opens up pores in the cell surface membrane of each bacterium for the plasmid to enter
Continued… • This transgenic bacterium will use the new gene to make insulin • Such bacteria can be isolated and grown in fermenters for mass production of insulin
Transferring a pest-resistant gene from bacterium to a crop plant • Created through the insertion of a gene to enable a crop plant to produce a chemical that kills insect pests • The vector is another bacterium that can infect plant cells but does not cause disease in the plant
Procedure 1. Use restriction enzymes to cut out the gene from the bacterial DNA to produce sticky ends 2. Use the same restriction enzyme to cut the plasmid to produce complementary sticky ends 3. Insert the gene into the plasmid 4. Insert the recombinant plasmid into the bacterium 5. Allow this bacterium to infect plant cells. Once inside the plant cells, the foreign gene will be inserted into the plant chromosome 6. Induce the plant cells to produce recombinant plants. A plant that has acquired a foreign gene is a transgenic plant
Groupwork In pairs, pen down your thoughts on • What are the advantages of growing pest- resistant plants? • What are the disadvantages of growing pest-resistant plants?
Advantages • Food production will be increased • May reduce environmental pollution as less pesticides are used Disadvantages • Insect pests may develop resistance to the poison produced by the plant • Pest resistance may be spread to weeds through cross pollination • Useful insects may be killed • Upsetting of the ecological balance
Advantages and Risks of Genetic Engineering
Groupwork In groups of 4, answer the following questions: • What are the benefits of genetic engineering? • What are the risks of genetic engineering?
Advantages of genetic engineering vs selective breeding Selective breeding Genetic Engineering Plants and animals need to be closely related or belong to the same species Gene from any plant or animal can be inserted in non-related species or different species 1. Both healthy and defective genes may be transmitted to the offspring Genes are carefully selected before transfer into an organism. This reduces the risk of genetic defects being passed on to the offspring 2. (i) Slow process (as it involves breeding over several generations) (ii) requires large areas of land/space Experiments with individual cells can reproduce rapidly in the laboratory in a small container 3. Less efficient e.g. organisms grow slowly and may require more food Increases productivity and efficiency in the breeding of organisms (increases profitability); e.g transgenic salmon grow faster and require less food than ordinary salmon 4.
Benefits of genetic engineering to society Applications of genetic engineering Benefits to society Low-cost production of medicines More affordable; more patients can get access to them and be treated e.g. human insulin Examples: • drought-resistant crops • salt-tolerant crops • crops that make more efficient use of nitrogen and other nutrients This allows farmers to grow crops even when the soil conditions are not suitable for cultivating most crops Production of crops that grow in extreme conditions (e.g. high salt environments)
Benefits of genetic engineering to society Applications of genetic engineering Benefits to society Development of • crops that produce toxins that kill insect pests; and • pesticide-resistant crops Development of foods designed to meet specific nutritional goals Use of costly pesticides that may damage the environment is reduced e.g. the Bt gene from a certain bacterium can be inserted into plants to produce a toxin that kills certain insect pests Improved quality of foods e.g. 2 genes of daffodil and one gene from the bacterium Erwinia uredarora inserted into rice plants produce ‘Golden Rice’ rich in vit. A
Social and Ethical Issues Surrounding Genetic Engineering 1. Environmental hazards (disrupts the environment) 2. Economic hazards (affect economies of society) 3. Health hazards (harm human health) 4. Social and Ethical hazards (affects the way an individual is looked upon in society) SHE3
1) Environmental hazards • Crop plant genetically engineered to i) produce insect toxins ii) be resistant to herbicides Effects of GM crops on environment: 1. Loss of biodiversity due to deaths of insects that feed on GM crops 2. Insects that feed on GM crops may adapt and develop resistance to the toxins/pesticides in these crops. 3. Herbicide resistant plants and weeds could cross-breed and create ‘superweeds’
2) Economic hazards 1. Patenting – the company legally owns the right to manufacture a product i.e. the company that 1st engineered the GM crop can control their use. This prevents unauthorized planting of such seeds without permission from the company. Patents prevent other biotechnology companies from producing the same type of GM seeds. Competition from farmers and other biotechnology companies is thus eliminated 2. Terminator technology – engineering of crop plants that produce seeds that cannot germinate, forcing farmers to buy special seeds from these companies every year. This poses a serious problem to poorer societies where farmers are struggling to make a living
3) Health hazards Introduction of allergens (substances that cause a reaction from the immune system) into food - e.g. protein lectin (effective pest control against aphids) has been transferred to potatoes - People who are allergic to lectin may unknowingly eat the transgenic potatoes and react badly to the lectin present Modifying a single gene in plants could result in the alteration of some metabolic processes within the plant - this may result in the production of toxins not usually found within these plants - The consumption of these plants or products made from these plants by humans can pose serious health problems 1. 2.
3) Health hazards 3. Genes that code for antibiotic resistance may accidentally be incorporated into bacteria that cause diseases to humans, making antibiotics ineffective in treating these diseases 4. Some people may deliberately create new combinations of genes which they use in chemical or biological warfare
4) Social and Ethical hazards 1. In gene therapy, a gene inserted into the body cells may find its way into the ova or sperms. If the gene mutates, it may affect the offspring of the patient 2. Genetic engineering may lead to class distinctions. Only individuals with sufficient financial means can afford certain gene technologies 3. Some religions do not approve of genetic engineering, as it may not be appropriate to alter the natural genetic make-up of organisms
Would this any of these be a reality one day?
TYS Questions a) Describe the process of large-scale production of insulin through medical biotechnology. [5] b) With reference to named examples, explain the social and ethical implications of genetic engineering? [5]
