Written Assignment 2

For thousands of years, humans have been practicing a relatively crude and slow form of genetic engineering—the manipulation of a species’ genome in ways that do not normally occur in nature. In its simplest form, genetic engineering is the careful selection of the plants or animals used as the breeders for a crop or animal population. Through this process, farmers and ranchers have produced meatier turkeys, seedless watermelons, and big, juicy corn kernels (Figure 7-8). But what used to take many generations of breeding now can be accomplished in a fraction of the time, using recombinant DNA technology, the combination of DNA from two or more sources into a product.

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Almost 10% of the world’s population suffers from vitamin A deficiency, which causes blindness in a quarter-million children each year and a host of other illnesses in people of all ages. These nutritional problems are especially severe in places such as southern Asia and sub-Saharan Africa, where rice is a staple of most diets. Addressing this global health issue, researchers have developed what may be the model for solving problems with biotechnology. It involves the creation of a new crop called “golden rice.” Humans and other mammals generally make vitamin A from beta-carotene, a substance found in abundance in most plants (it’s what makes carrots orange), but not in the edible part of rice grains. To introduce beta-carotene into rice crops, researchers used recombinant DNA technology to insert three genes into the rice genome that code for the enzymes used in the production of beta-carotene. Two of the transplanted genes were from the daffodil plant and one was a bacterial gene. As the transplanted genes are expressed, the rice grain takes on a golden color from the accumulated beta-carotene. Since golden rice was first developed in 1999, new lines have been created that produce almost 25 times the vitamin A found in the original strains. Field tests of golden rice are still in progress, and it is viewed as one of the most promising applications yet of biotechnology. Precautionary biosafety protocols and regulations, however, have restricted its cultivation by large-scale commercial farms. In June 2016, 110 Nobel laureates signed a letter urging an end to the opposition to GMOs, highlighting the potential value of golden rice, in particular.

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In the United States, biotechnology has already had a profound impact on agricultural practices. It is not a stretch to say that we are in the midst of another green revolution, but that few people are aware of it. The numbers are surprising: 92% of all corn grown in the United States is genetically modified; 94% percent of all cotton grown is genetically modified; and 94% of all soybeans grown are genetically modified. Two factors explain much of the extensive adoption of genetically modified plants in U.S. agriculture: 1) Many plants have had insecticides engineered into them, which can reduce the amounts of

insecticides used in agriculture. 2) Many plants also have herbicide-resistance genes engineered into them. Such herbicide-

resistant plants (as well as insect-resistant plants) can reduce the amount of plowing required around crops to remove weeds. As a consequence, then, the use of genetically modified plants can reduce both the costs of producing food and the loss of topsoil to erosion.

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Every year, about 40 million tons of corn is deemed unmarketable as a consequence of insect damage. Increasingly, however, farmers have been enjoying greater success in their battles against insect pests. Farmers owe much of this success to soil-dwelling bacteria of the species Bacillus thuringiensis (Bt), which produce spores containing crystals that are fatally poisonous to insects but harmless to the crop plants and to people Beginning in 1961, the toxic “Bt” crystals were included in pesticides that were sprayed on plants. In 1995, however, recombinant DNA technology led to a huge improvement. The gene coding for the production of the Bt crystals was inserted directly into the DNA of many different crop plants, including corn, cotton, and potatoes, so that the plants themselves produced the crystals. Farmers owe much of this success to soil-dwelling bacteria of the species Bacillus thuringiensis. These bacteria produce spores containing crystals that are highly poisonous to insects but harmless to the crop plants and people. Within an hour of ingesting the crystals, the insect’s feeding is disrupted. The toxic crystals cause pores to develop throughout the insects’ digestive system, paralyzing their gut and making them unable to feed. Within a few days, the insects die from a combination of tissue damage and starvation. There is no evidence that humans are harmed by the Bt crystals, even when they are exposed to very high levels.

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In the fight against weeds, bacteria have proven very useful. In the 1990s, researchers discovered a bacterial gene that confers resistance to herbicides. Integration of this gene into the plants’ DNA gives the crops resistance to herbicides, allowing farmers to kill weeds with herbicides while leaving the crop plants unharmed (Figure 7-12).

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Agriculture includes the cultivation not just of plants but also of animals. And for the first time, the U.S. Food and Drug Administration is close to approving for human consumption a genetically modified animal. The animal in question is a transgenic Atlantic salmon that carries a growth hormone gene from another species (Chinook salmon), along with a region of DNA from a third species (ocean pout) that acts as an “on” switch, facilitating transcription of the growth hormone gene. The transgenic fish, which is reported by its creators to taste the same as regular Atlantic salmon, grows much more quickly and reaches market size within 18 months rather than the usual three years. The FDA has reported that the transgenic salmon “is as safe to eat as food from other Atlantic salmon.” Numerous fisheries experts, food safety experts, environmental groups, and consumer groups, however, continue to express concerns about a wide variety of safety and environmental issues and the process by which the safety and environmental impacts of the transgenic species have been evaluated. Health concerns include the possibility that consuming the salmon will cause increased rates of allergic reactions, as well as unknown effects that may stem from potentially higher levels of hormones present in the fish. Most troubling to environmental groups is the risk that the larger, faster-growing transgenic fish will escape from their enclosed breeding facilities into their natural habitat—something that many experts believe is inevitable. If this occurs, environmentalists fear that the fish might harm wild salmon populations, many of which are listed as endangered, because the transgenic salmon can consume more resources and may grow too large to be consumed by its natural predators. It is unclear what the outcome would be.

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Chickens without feathers look ridiculous. But such a genetically modified breed was developed with a valuable purpose in mind: “naked” birds are easier and less expensive to prepare for market, benefiting farmers by lowering their costs and consumers by lowering prices. Such chickens, however, turned out to be unusually vulnerable to mosquito attacks, parasites, and disease, and ultra-sensitive to sunlight. They also have difficulty mating since the males are unable to flap their wings. These chickens teach us an important lesson about genetically modified plants and animals. Although the new breed of featherless chickens was produced by traditional animal husbandry methods—the cross-breeding of two different types of chickens—as opposed to using recombinant DNA technology, the new breed ended up having not just the desired trait of no feathers, but it also had some unintended and undesirable traits. Now as more genetically modified foods are created using modern methods of recombinant DNA technology, the same risks of unintended and potentially harmful traits occurring must be weighed. For these and other reasons—some legitimate and rational, others irrational—many people have concerns about the production and consumption of genetically modified foods.

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Concern: Safety of Eating Genetically Modified Foods The concern about the safety of eating GMOs was addressed in 2016, in a report by the National Academy of Sciences (NAS), an independent organization of the most distinguished experts in science. In this careful and detailed 606-page report, the NAS examined epidemiological data on cancer rates and other human-health problems and concluded that there was no evidence that foods from genetically engineered crops were less safe than those from non-genetically engineered crops. The NAS also noted that a large number of experimental studies provided reason-able evidence that animals, too, were not harmed by eating food derived from genetically modified crops. Concern: Invincibility of Organisms That We Want to Kill Herbicide-resistant canola plants were cultivated in Canada, making it possible for farmers to apply herbicides freely to kill the weeds but not the canola crop. But the herbicide-resistant canola plants accidentally spread to neighboring farms and grew out of control, because traditional herbicides could not kill them. Similarly, there has been concern that insect pests will develop resistance to the Bt produced by genetically modified crops, which will also make these pests resistant to Bt pesticides applied to crops that are not genetically modified. In the NAS report, scientists noted that insects have been slow to evolve resistance and resistance- management strategies have been effective. Overall, they found no conclusive evidence of cause-and-effect relationships between genetically engineered crops and environmental problems. Concern: Adequate Testing and Regulation of GMOs It is impossible to really know whether a new technology has been tested adequately. Scientists and lawmakers have been working toward a responsible set of policies designed to ensure that sufficient safety testing is done. For example, laboratory procedures for working with recombinant DNA have been established, and researchers have developed techniques that make it impossible for most genetically engineered organisms to survive outside the specific condi-tions for which they are developed. Additionally, regulatory strategies vary from country to country. 23

Concern: Loss of Genetic Diversity Among Crop Plants As increasing numbers of farmers favor one or a few genetically modified strains of crops, the genetic diversity of the crops declines. This can increase the vulnerability of crops to environmental changes or pests. For example, in the mid-1800s, much of the population of Ireland depended on a diet of potatoes. Because most of the potato crops had been propagated from cuttings from the same plant, they were all genetically the same. When the crops were infected by a mold specific to that one crop, most were wiped out, causing the Irish Potato Famine, which was ultimately responsible for the deaths of more than a million people. Concern: Hidden Costs of GMOs When seed companies create genetically modified seeds with crop traits desirable to farmers, the companies also engineer sterility into the seeds. As a consequence, the farmers are dependent on seed companies and must purchase new seeds for each generation of their crops. In most situations, however, seed costs are only a small fraction of the total costs of crop production. Concern: Unnatural Substances Are Necessarily Harmful Some argue that genetically modified foods are not natural and, for that reason, must be harmful. This argument—called the naturalistic fallacy—is a common, but flawed, argument and should not be a cause for concern.

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From a scientific perspective, the question of whether genetically modified foods are safe is not the right question to ask. Instead, we must ask a specific question about a potential danger and figure out a way to approach it. Furthermore, no single research study that fails to find a danger of genetically modified food will conclusively resolve the issue. Rather, each such study adds to a body of evidence that, cumulatively, can give us confidence in GMO safety. Humans live a long time. Is there a practical way to evaluate the risks of long-term consumption of genetically modified food? It’s just not feasible to conduct a whole lifespan study—70 years or more—involving hundreds or thousands of humans. So researchers used a shorter-lived mammal: rats. They randomly divided 180 rats into three groups. The first group consumed a diet high in a genetically modified rice (engineered to be insect-resistant); the second consumed a diet high in non–genetically modified rice, but otherwise equal in nutrients; and the third consumed a non–rice-based diet.

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The researchers measured the mortality rates of the rat groups for 18 months and found no differences among the three groups. Similarly, they found no differences in the number of tumors or other types of organ damage. The researchers noted that the amount of genetically modified rice consumed by a rat in the first group was approximately 10 times greater (in proportion to body weight) than would be consumed by a human. What happens when conflicting results are reported for other, seemingly similar studies? Let’s look at an example. For two years, another team of researchers fed rats a diet containing one of three different amounts of genetically modified corn, and evaluated health effects and mortality rates. The researchers also included groups of rats fed genetically modified corn that had been treated with a pesticide, and other groups of rats fed non-genetically modified corn that had been exposed to pesticide. The control group was fed non–genetically modified corn that had not been exposed to pesticide. The reported results were dramatic and received widespread media coverage. The rats consuming the genetically modified corn were reported to have significantly higher mortality rates and higher incidence of tumors. But closer inspection of the study design generated a huge and critical response from other researchers.

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Critics focused on a couple of important methodological problems. First, the researchers had used a strain of rat known to have an unusually high incidence of tumors. This made it difficult to know whether the differences between groups were caused by the genetically modified corn or were just normal variation. Second, the large number of treatment (experimental) groups were made up of very small sample sizes: 10 different groups of males and 10 groups of females, with just 10 animals in each experimental group. As a result, the differences between groups reported by the researchers were not statistically significant. Furthermore, the researchers did not include the relevant statistical analyses. When other researchers extracted data from figures in the published report and conducted their own careful statistical analyses, they concluded that the results provided no evidence at all that consumption of genetically modified corn had adverse effects on health. They even noted that by “cherry picking” the results to report—as the original researchers had done—they could state that males in the control groups had a mortality rate three times higher than the two groups consuming the most genetically modified corn. In response to reevaluations of the data, the editor-in-chief of the journal (Food and Chemical Toxicology) retracted the published article.

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The significant media attention received by this study prior to its being discredited highlights the challenge in trying to prove that something is not dangerous. Just a single paper making an untrue assertion about the adverse effects of genetically modified food on health can arouse deep public fear. The issue of the safety of foods containing GMOs continues to be debated. Research, and the accumulation of evidence that genetically modified foods do not pose health risks, continues. This process is central to the power of scientific thinking. The consensus that genetically modified foods carry no more risk than non–genetically modified foods is endorsed by many organizations (that have no obvious financial stake in the outcome), including the U.S. National Academy of Sciences, the World Health Organization, the American Medical Association, and the British Royal Society.

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