Chapter 20 Molecular Genetics Lesson 3 - Genetic Engineering


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Chapter 20 Molecular Genetics Lesson 3 - Genetic Engineering

  1. 1. Genetic Engineering Definition: a technique used to transfer genes from one organism to another
  2. 2. Lesson Objectives <ul><li>(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 </li></ul><ul><li>(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 </li></ul><ul><li>(h) outline the process of large-scale production of insulin using fermenters </li></ul><ul><li>discuss the social and ethical implications of genetic engineering, with reference to a named example </li></ul><ul><li>Use the knowledge gained in this section in new situations or to solve related problems. </li></ul>
  3. 3. How does genetic engineering work? <ul><li>Individual genes cut off from cells of one organism and inserted into the cells of another organism of the same/ different species using vectors </li></ul><ul><li>Plasmid : circular DNA from bacteria used to transfer genes; is an example of a vector </li></ul><ul><li>The transferred gene can express itself in the genetically engineered organism </li></ul>
  4. 4. Restriction enzymes <ul><li>enzyme that cuts double-stranded DNA </li></ul><ul><li>enzyme makes two incisions, one through each of the phosphate backbones of the double helix without damaging the bases </li></ul><ul><li>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 </li></ul>
  5. 5. Types of restriction enzymes
  6. 6. Genetic Engineering Applications
  7. 7. Diabetes mellitus <ul><li>Body unable to control its blood glucose conc. within safe limits </li></ul><ul><li>Kidney unable to reabsorb all the glucose </li></ul><ul><li>Glucose not reabsorbed is excreted in the urine </li></ul><ul><li>2 main types: </li></ul><ul><li>Type 1 </li></ul><ul><li>Type 2 </li></ul>
  8. 8. Type 1 diabetes <ul><li>Juvenile/early-onset diabetes (occurs early in life) </li></ul><ul><li>Due to inability of pancreas to produce sufficient insulin </li></ul>
  9. 9. Transferring the human insulin gene into bacteria <ul><li>Obtain the human chromosome containing the insulin gene. </li></ul><ul><li>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 </li></ul><ul><li>Obtain a plasmid from a bacterium. </li></ul><ul><li>Cut the plasmid with the same restriction enzyme. This produces complementary sticky ends </li></ul><ul><li>Mix the plasmid with the DNA fragment containing the insulin gene. </li></ul><ul><li>Add DNA ligase to join the insulin gene to the plasmid </li></ul><ul><li>Mix the plasmid with E.coli bacteria . </li></ul><ul><li>Apply temporary heat or electric shock . This opens up pores in the cell surface membrane of each bacterium for the plasmid to enter </li></ul>
  10. 11. Industrial fermenter <ul><li>a giant steel cylindrical tank closed at both ends </li></ul><ul><li>designed to keep the internal environment favourable for the desired biological process to operate </li></ul><ul><li>may be designed for aerobic OR anaerobic processes </li></ul>
  11. 12. Features of a fermenter used for aerobic processes <ul><li>(1) Cooling system </li></ul><ul><li>- Internal coils where water flows through a cooling jacket to remove heat from the culture broth </li></ul><ul><li>- maintains a suitable temperature for microbial growth and activities </li></ul><ul><li>- a temperature probe is used to measure the temperature of the broth </li></ul>
  12. 13. Features of a fermenter used for aerobic processes <ul><li>(2) Aeration system (addition of air to a liquid ) </li></ul><ul><li>(I) Sparger </li></ul><ul><li>metal ring with tiny holes through which air is passed into the fermenter under high pressure </li></ul><ul><li>air enters fermenter as tiny air bubbles (provides large s.a.:volume ratio for O 2 to dissolve in the nutrient broth) </li></ul><ul><li>O 2 diffuses into the nutrient broth </li></ul><ul><li>(II) Impeller (stirring device) </li></ul><ul><li>Mixes the air bubbles with the nutrient broth (culture medium) </li></ul><ul><li>Ensures O 2 and nutrients are evenly distributed for use by bacteria in all parts of the fermenter </li></ul><ul><li>Continuous stirring also ensures that the growing bacteria do not clump together </li></ul>
  13. 14. Features of a fermenter used for aerobic processes <ul><li>(3) pH controller </li></ul><ul><li>ensures that pH is kept optimum for maximum growth of the microorganism </li></ul><ul><li>The pH probe measures the pH of the broth and is adjusted using the acid/base reservoir </li></ul><ul><li>(4) Nutrients </li></ul><ul><li>The nutrient broth should contain: </li></ul><ul><li>a carbon source and energy source e.g. glucose </li></ul><ul><li>a nitrogen source e.g. a.a., nitrates or ammonium compounds </li></ul><ul><li>essential mineral salts </li></ul>
  14. 15. Features of an industrial fermenter sparger sparger impeller
  15. 16. Human insulin production in large-scale fermenters <ul><li>Transgenic bacteria containing the human insulin gene are mixed with a nutrient broth inside the fermenter </li></ul><ul><li>To culture the transgenic bacteria under optimum conditions, O 2 conc., pH, temperature, conc. of nutrients are carefully monitored by a computer </li></ul><ul><li>The transgenic bacteria are able to multiply rapidly to form a large population that produces large quantities of insulin </li></ul><ul><li>The bacteria are removed from the broth. They are burst open to release the insulin. The insulin is extracted and purified </li></ul>
  16. 17. Advantages of using insulin produced by genetic engineering <ul><li>Previously, insulin was obtained from the pancreas of slaughtered animals. However </li></ul><ul><li>(i) animal insulin is not the same as human insulin </li></ul><ul><li>(ii) many diabetics develop antibodies against animal insulin after prolonged treatment . Such patients can no longer use animal insulin to control their diabetes </li></ul><ul><li>(iii) diseases may be transmitted from animals to humans who use animal insulin </li></ul><ul><li>Genetically engineered bacteria multiply rapidly (cultured in large sterile fermenters under ideal conditions) to form a huge population which makes large quantities of the gene product (insulin). Insulin is extracted and purified. </li></ul><ul><li>The new insulin (produced by genetic engineering) is exactly the same as ordinary human insulin (therefore the problem associated with use of animal insulin is not likely to arise) </li></ul>
  17. 18. Transgenic plants
  18. 19. Transgenic plants <ul><li>Created through the insertion of a gene to make a crop plant resistant to herbicides </li></ul><ul><li>This allows weeds to be killed by herbicide without affecting the crop plant </li></ul>
  19. 20. e.g.Tobacco plants <ul><li>A weak solution of cyanamide kills weeds but also causes some damage to tobacco plants </li></ul><ul><li>A soil fungus, Myrothecium verrucaria , has a gene which produces an enzyme, cyanamide hydratase , which converts cyanamide to urea (which is harmless to tobacco plants) </li></ul><ul><li>Hence this gene can be inserted into tobacco plants, making them </li></ul><ul><li>(i) resistant to the herbicide and </li></ul><ul><li>(ii) the urea formed provides a source of nitrogen for plant growth </li></ul>
  20. 22. Transgenic plants
  21. 23. Transferring genes within the same species <ul><li>Genes that confer resistance to pests can be cut from a wild plant and inserted into a crop plant e.g. wild species wheat into common wheat confers resistance to the Hessian fly (a major wheat pest) </li></ul><ul><li>Genes can also be transferred between people. Healthy genes from one person can be inserted into the cells of another person with defective genes ( gene therapy ). This is used to treat certain diseases e.g. lung disease cystic fibrosis, where bronchial tubes produce mucus that blocks up the respiratory system, making it difficult to breathe </li></ul><ul><li>Cystic fibrosis may be treated by directly replacing defective genes in damaged airways cells with healthy genes </li></ul>
  22. 24. Summary
  23. 25. Advantages and Risks of Genetic Engineering
  24. 26. Groupwork <ul><li>In groups of 4, pen down your thoughts on </li></ul><ul><li>What are the benefits of genetic engineering? </li></ul><ul><li>What are the risks of genetic engineering? </li></ul>
  25. 27. Advantages of genetic engineering vs selective breeding Increases productivity and efficiency in the breeding of organisms (increases profitability); e.g transgenic salmon grow faster and require less food than ordinary salmon Less efficient e.g. organisms grow slowly and may require more food 4. Experiments with individual cells can reproduce rapidly in the laboratory in a small container (i) Slow process (as it involves breeding over several generations) (ii) requires large areas of land/space 3. Genes are carefully selected before transfer into an organism. This reduces the risk of genetic defects being passed on to the offspring Both healthy and defective genes may be transmitted to the offspring 2. Gene from any plant or animal can be inserted in non-related species or different species Plants and animals need to be closely related or belong to the same species 1. Genetic Engineering Selective breeding
  26. 28. Benefits of genetic engineering to society <ul><li>Examples: </li></ul><ul><li>drought-resistant crops </li></ul><ul><li>salt-tolerant crops </li></ul><ul><li>crops that make more efficient use of nitrogen and other nutrients </li></ul><ul><li>This allows farmers to grow crops even when the soil conditions are not suitable for cultivating most crops </li></ul>Production of crops that grow in extreme conditions (e.g. high salt environments) More affordable; more patients can get access to them and be treated e.g. human insulin Low-cost production of medicines Benefits to society Applications of genetic engineering
  27. 29. Benefits of genetic engineering to society 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 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 <ul><li>Development of </li></ul><ul><li>crops that produce toxins that kill insect pests; and </li></ul><ul><li>pesticide-resistant crops </li></ul>Benefits to society Applications of genetic engineering
  28. 30. Social and Ethical Issues Surrounding Genetic Engineering <ul><li>E nvironmental hazards (disrupts the environment) </li></ul><ul><li>E conomic hazards (affect economies of society) </li></ul><ul><li>H ealth hazards (harm human health) </li></ul><ul><li>S ocial and E thical hazards (affects the way an individual is looked upon in society) </li></ul>SHE 3
  29. 31. 1) E nvironmental hazards <ul><li>Crop plant genetically engineered to </li></ul><ul><li>i) produce insect toxins </li></ul><ul><li>ii) be resistant to herbicides </li></ul><ul><li>Effects of GM crops on environment: </li></ul><ul><li>Loss of biodiversity due to deaths of insects that feed on GM crops </li></ul><ul><li>Insects that feed on GM crops may adapt and develop resistance to the toxins/pesticides in these crops. </li></ul><ul><li>Herbicide resistant plants and weeds could cross-breed and create ‘superweeds’ </li></ul>
  30. 32. 2) E conomic hazards <ul><li>Patenting – the company legally owns the right to manufacture a product i.e. the company that 1 st 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 </li></ul><ul><li>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 </li></ul>
  31. 33. 3) H ealth hazards <ul><li>Introduction of allergens (substances that cause a reaction from the immune system) into food </li></ul><ul><li>- e.g. protein lectin (effective pest control against aphids) has been transferred to potatoes </li></ul><ul><li>- People who are allergic to lectin may unknowingly eat the transgenic potatoes and react badly to the lectin present </li></ul><ul><li>Modifying a single gene in plants could result in the alteration of some metabolic processes within the plant </li></ul><ul><li>- this may result in the production of toxins not usually found within these plants </li></ul><ul><li>- The consumption of these plants or products made from these plants by humans can pose serious health problems </li></ul>
  32. 34. 3) H ealth hazards <ul><li>Genes that code for antibiotic resistance may accidentally be incorporated into bacteria that cause diseases to humans, making antibiotics ineffective in treating these diseases </li></ul><ul><li>Some people may deliberately create new combinations of genes which they use in chemical or biological warfare </li></ul>
  33. 35. 4) S ocial and E thical hazards <ul><li>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 </li></ul><ul><li>Genetic engineering may lead to class distinctions . Only individuals with sufficient financial means can afford certain gene technologies </li></ul><ul><li>Some religions do not approve of genetic engineering, as it may not be appropriate to alter the natural genetic make-up of organisms </li></ul>
  34. 36. Would this any of these be a reality one day?
  35. 41. Can Jurassic Park become a reality than?
  36. 42. References <ul><li> </li></ul>
  37. 43. TYS Questions <ul><li>Describe the process of large-scale production of insulin through medical biotechnology. [5] </li></ul><ul><li>With reference to named examples, explain the social and ethical implications of genetic engineering? [5] </li></ul>