Genetic Engineering: Redesigning Life PDF

8.3 Genetic Engineering: Redesigning Life For centuries, people have bred plants and animals to get the best characteristics in...

8.3 Genetic Engineering: Redesigning Life For centuries, people have bred plants and animals to get the best characteristics in the progeny. Before Mendel’s pea experiments, people mated a prolific egg-laying hen with a strong rooster, a good milk-producing cow with a closely related bull, and a large flower with a colourful flower. They saved and replanted the grains of the best- yielding wheat. Their efforts resulted in the varieties of livestock, vegetables, flowers, and field crops that we see today. Farmers now tend to grow the varieties that are easiest to grow, store, and ship; that are resistant to pests; and that give the best yields under their environmental conditions. As a result, some varieties of agricultural plants and animals are no longer planted or raised—they are no longer good economic choices for farmers. However, in Canada and other countries, there is now a movement to raise and protect these “heirloom varieties.” An heirloom variety is a variety of a species that was grown for a long time but is no longer commercially produced. For example, gardeners raise Figure 1 Heirloom tomatoes can be heirloom tomatoes (Figure 1), and hobby farmers raise endangered horse popula- quite different from the tomatoes you tions. Maintaining production of these varieties preserves the genetic diversity of their usually see in stores. species. If a disease suddenly wipes out cabbage crops, for example, one or more of the heritage varieties might be resistant to this disease. Agronomists would propagate these plants and breed them with other cabbage plants to give their disease resistance to all cabbage plants. Alternatively, agronomists might extract the gene for disease resistance from the healthy plants and insert it into other cabbage plants. Biopharming Genetic engineering uses DNA technology to modify the genes of a cell or an organism. Molecular biologists can introduce new functions into an organism. An early demonstration of genetic engineering is the glowing tobacco plant shown in Figure 2. Today, scientists use genetic engineering to find cures for various diseases that affect animals and plants. Perhaps most useful is the introduction of one or more genes from one organism into another. This could cause the host organism to pro- duce a certain protein, such as insulin, that is useful to us. When such pharmaceutical products are produced on a large scale, the process is called biopharming. Some biopharming methods involve the genetic engineering of organisms to pro- duce a target protein. For example, cattle have been genetically engineered to produce a target protein in their milk, and safflower plants have been genetically engineered to produce such a protein in their seeds. Some genetically modified goats are able to Figure 2 Genetic engineering can produce spider silk proteins in their milk. These proteins can be removed from the produce some very wild results. This milk and used in manufacturing. The genetic change is engineered in the germ line tobacco plant glows because a firefly of the species, and the ability to make the new protein is passed on to the offspring gene, which encodes for the enzyme of the original genetically engineered goat. Thus, there can be an entire herd of bio- luciferase, has been inserted into its DNA. pharming dairy goats! Medically important proteins, such as the life-saving antico- agulant antithrombin, can be produced quite inexpensively by genetic engineering, biopharming a process in which compared with using laboratory techniques. genetically engineered host organisms are Although this biotechnology is promising, it should be approached with caution. used to make pharmaceuticals or other Even a minor change in an animal’s genome may prove to have negative conse- products that are useful to humans quences in the future, such as to an animal’s long-term health. Transgenic Organisms: Altered DNA transgenic organism (genetically An organism that has been changed by scientists to contain one or more genes from modified organism, GMO) an organism another organism is known as a transgenic organism or a genetically modified organism (GMO). that has been modified to carry genes it The E. coli bacteria that were altered to become insulin factories are an example of does not normally carry a GMO. 386   Chapter 8 Genetic Technologies NEL 8159_Bio_Ch08_pp364-421.indd 386 3/27/12 6:03 PM  More recent developments in insulin production may be even cheaper and faster than the bacterial methods discussed earlier. For example, genetic engineers at the University of Calgary have discovered how to get safflowers to produce insulin. The DNA is easily manipulated, and the desired product(s) can be harvested in the oil from the seeds. Safflower is an easily grown thistle-like plant that prefers arid condi- tions (Figure 3). Maurice Moloney was one of the scientists behind the genetic engi- neering of safflower-produced insulin. At an agricultural biotechnology conference in Saskatoon, Saskatchewan, he explained how plants could be used to produce a biodegradable plastic called polyhydroxybutyrate (PHB): WEB LINK PHB is a biopolymer produced in certain bacteria. PHB production requires the intervention of three enzymes. Plants lack these enzymes, but the bacterial genes specifying these biochemical conversions have Figure 3 A safflower, the plant from been expressed in plants. The result is that a significant amount of carbon which genetic engineers are now metabolism is re-routed into the production of PHB. harvesting insulin One of the main factors limiting the wide use of PHB polymers as an environmentally benign plastic is the cost of production in microorgan- isms. Production in plants could address this problem and render PHB an economically viable material for production of milk containers, plastic bags, and a variety of disposable packaging. Why Use Transgenic Plants and Animals? Why did scientists not stick with bacteria to produce insulin and other genetically engineered products? Why have they researched the use of goats and plants as protein factories? One reason for the expanding research is cost. Animal- and plant-based methods are usually more economical than operating a laboratory with controlled bacterial populations. As a result, the cheaper insulin from safflowers, for example, could improve the lives of diabetics in the developing world, where many people cannot afford insulin at the current prices. Since 5 % of deaths worldwide are attributed to diabetes, the production and availability of less expensive insulin is an important goal. A second reason why plants and animals may be better to use than bacteria is that larger organisms can produce larger molecules. Transgenic goats can produce larger proteins, with more complex folding patterns, than bacteria can. Other transgenic organisms are engineered to be bigger and/or better versions of themselves, which is usually considered to be a benefit commercially (Table 1). Many other organisms are still being developed (Table 2). CAREER LINK Table 1 GMOs Commercially Available in Canada and Table 2 Some GMOs Currently under Their Benefits Research Genetically Organism Benefit modified organism Benefit rice better vitamin coho salmon faster maturation content (specifically, betacarotene) cattle resistance to mad cow disease tobacco hepatitis B vaccine tomatoes better travel durability between field, store, and table; corn oral vaccines better flavour canola resistant to herbicides and pests; altered fatty acid composition corn resistance to pests soybeans herbicide tolerance (so that weeds can be sprayed without affecting the soybean plants) NEL 8.3 Genetic Engineering: Redesigning Life    387 8159_Bio_Ch08_pp364-421.indd 387 3/27/12 6:03 PM  Transgenic Plants Genetically modified (GM) canola and other field crops have been engineered to be resistant to specific herbicides. This technology means that herbicides can be sprayed to kill weeds but the crop plant remains healthy. The oil from the genetically modified canola plant is identical to conventional canola seed oil. Approximately 80 % of the western Canada canola crop is the genetically modified variety. Farmers spend about 40 % less on herbicides for GM canola crops, versus conventional canola crops, and they report up to a 10 % increase in yield. An advantage of GM plants is their potential to provide food for millions of hungry people in the developing world. A major drawback of GMOs is the increased cost of the patented seeds, making them unaffordable to some farmers. For a family in the developing world, however, having higher-yielding and pest-resistant crops might mean the difference between hunger and a better life. Knockout Mice Knockout mice are produced by genetic engineering to have at least one gene com- pletely turned off by a mutation. They are used to study the purpose of each gene and to draw parallels to humans. Knockout mice have been very useful in learning about the effects of certain genes on human health, since the mouse genome is quite similar to the human genome. Knockout mice are not actually “knocked out.” They are simply homozygous for one particular gene. Both copies of this gene are altered to a non-functional state so that scientists can study the effects on a mouse without it. Sometimes, an alteration does not seem to cause any change in the structure or function of the mouse. Other times, a loss of gene function significantly changes the phenotype. For example, in one mouse, scientists knocked out the p53 gene, which helps to stop tumour growth. Scientists have discovered that humans are more likely to get certain cancers if they have a mutation in this gene. The p53 knockout mice got cancers, but not in exactly the same tissues as humans with the mutation do. Much useful research is accomplished with this method, even though the expression of the genes may vary. Societal Concerns and Implications If you could save lives by producing vaccines in transgenic bananas, would you? Deciding exactly where to draw the line on transgenic organisms is difficult. There is no doubt that there are many benefits, but what about the risks? Because of the potential ramifications of GMOs, societies and governments are moving cautiously. Genetic engineering is a new biotechnology, and, as a result, many people, including scientists, are concerned that there may be far-reaching irreversible effects. For example, a genetically modified organism such as GM canola might outcompete native or non-modified species. Being resistant to herbicides, the organism could become a weed itself. None of this has yet been proven, but some governments, including the Canadian government and several in the European Union, are concerned. Competition is not the only concern. People are also asking whether crops or ani- mals that produce medical products might interbreed with native plants or animals. The proximity of GMO farms to traditional and organic farms is a concern because of potential cross-pollination and contamination. Another concern is that GM plants might contain toxins and harm any animals that eat them. Some medicine-producing safflowers, for example, are poisonous. Intense herbicide application on herbicide-resistant GM crops is a concern due to potential soil and water contamination. This could be especially problematic for drinking water supplies and organisms living in nearby lakes and streams. GMOs are often advertised as reducing the need for pesticides. However, it is difficult to make general statements given that each plant species reacts differently under different conditions. 388   Chapter 8 Genetic Technologies NEL 8159_Bio_Ch08_pp364-421.indd 388 3/27/12 6:03 PM  Transgenic fish in aquaculture tanks have escaped and mixed with wild species in the ecosystem. While the transgenic fish had mating advantages over the wild spe- cies, the offspring of the transgenic fish were not as viable as the wild fish offspring. Thus, the transgenic fish reduced the population of the fish species overall. Regulations vary a great deal, depending on the country developing the GMOs. North America and Europe have a rigorous testing and approval process, and crops are often not released for up to 10 years. In contrast, China’s government allows the immediate release of some GM crops. This could have huge implications for envi- ronmental protection if adequate testing is not required prior to implementation in the field. A further concern is related more to politics and society than to science: Should the inventors of the technology be allowed to reap a profit indefinitely? If so, at what cost to the environment or the public? A main concern with genetically modified seeds is the power given to patent holders. Farmers are not allowed to save seeds from their crop for the next year because the companies with the patents want them to buy new seeds. Should this kind of policing of patents be allowed, or should the patent laws be changed to make GMO technology more public? To date, extensive lawsuits over patented seeds have been filed by GMO companies that have strict contracts with farmers. Consumer groups would like to see the Canadian Food Inspection Agency change labelling rules so that consumers can decide for themselves whether they want to buy a product that contains a GMO. The applications of genetic engineering already include biofuel production, food processing, sewage treatment, drug development, and pollution control. What else will the future bring? Research This Analyzing Concerns about GMOs Skills: Questioning, Researching, Analyzing, Evaluating, Communicating, skills Defining the Issue, Defending the Decision handbook A4.1, A4.2 As discussed in this section, GMOs are increasingly being used for medical applications and food supplies. However, there are many concerns with GMOs. 1. Choose a GMO from Table 1 or 2 on page 387 or another GMO that interests you. Research this GMO, its applications, its benefits, and any concerns for society and the environment. A. Are the concerns about the application of this GMO valid? Provide reasons for your decision. Your reasons may include societal, cultural, economic, political, and environmental implications. T/I B. Even with the potential concerns, do you believe that the GMO should continue to be used? Provide reasons for your decision. T/I C. From the viewpoint of a government scientist, write a summary for the Ministry of the Environment about the pros and cons of the GMO. Include your recommendations for the use of this technology. T/I C WEB LINK NEL 8.3 Genetic Engineering: Redesigning Life    389 8159_Bio_Ch08_pp364-421.indd 389 3/27/12 6:03 PM  8.3 Review Summary Genetic engineering produces transgenic, or genetically modified, organisms (GMOs) by inserting DNA from one species into another species. GMOs offer many benefits for humans, such as higher crop yields and lower dependence on herbicides and pesticides. Plants and animals, rather than bacteria, are often used in genetic engineering because they are more economical to maintain and they can produce larger molecules. Because genetic engineering is a new biotechnology, many people are concerned that there may be far-reaching, irreversibly harmful effects. Questions 1. What are heirloom varieties of plants or animals? 10. Choose one GMO, and research the benefits and Why is it important that they be preserved? K/U risks associated with it. Summarize your findings, 2. List the potential benefits of biopharming for and then give your opinion about whether this is a developing countries. T/I good technology to pursue. T/I C A 3. What is a transgenic organism? List at least three 11. In Canadian patent law regarding biopharming, the plant species and two animal species that have been legislation prevents patenting “higher” genetically genetically modified, as well as the purpose for each modified organisms. Using the Internet, research modification. K/U how Canadian law defines a “higher organism” and how the Supreme Court has ruled on patenting 4. Transgenic goats are very different from transgenic GMOs in Canada. T/I bacteria. Why would scientists choose to develop a transgenic goat, not a transgenic bacterium, to 12. Suppose you are a researcher at Agriculture and produce a protein? K/U Agri-Food Canada and you want to remove the gene that prevents fish from freezing in sub-zero 5. What is a knockout mouse? What are some benefits temperatures and place it in a tobacco plant. Your of using knockout mice in scientific research? K/U goal is to have the plant produce the “antifreeze” 6. List some concerns that people have with transgenic protein to protect it from frost. K/U T/I C organisms. List some personal concerns. K/U T/I C (a) Draw a flow chart that summarizes the steps in 7. Look at Tables 1 and 2 on page 387. Do you support this genetic technology. these initiatives? Explain why or why not. T/I C (b) Discuss the economic advantage of this 8. Currently there is a big push from environmentalists technology for tobacco farmers. and the public to include information about any (c) Suggest one ethical issue that may arise from genetically modified organisms used in our food. this technology. Use a t-chart to identify the pros and cons of including GMO information on food labels. T/I C WEB LINK 9. Research the role of the Canadian Food Inspection Agency with respect to genetic engineering. What does this agency do? How much power does it have in steering the direction of food science research in Canada? T/I C 390   Chapter 8 Genetic Technologies NEL 8159_Bio_Ch08_pp364-421.indd 390 3/27/12 6:03 PM