Manipulating the genetic material of different organisms can have interesting consequences. While some changes are innocuous like vegetables with longer shelf-lives than the nature intended, others are spooky like mice that glow in dark. Humans have been carrying out such manipulations for centuries.
The primary focus of domesticating crops and animals was to increase the production, geographic range, palatability and several other characteristics. Today we have tools to carry out these changes more quickly. Read on to find out about the benefits of selective breeding, which has been used historically vs genetic engineering. What are the problems, if any, that are associated with manipulating genes for our benefit?
One of the earliest domesticated plants was the bottle gourd. By 10,000 BC the domesticated version of this plant was used as food and to make containers. Several other crops such as peas and wheat were domesticated to increase their seed and grain size. This process of domesticating plants and crossing them, known as selective breeding, enabled humans to improve the offspring by selecting for desirable traits. Selective breeding is the precursor to modern techniques of genetic modification. The use of selective breeding resulted in crops that were unrecognizable from the parent plant.
The process of selective breeding improved vastly in the 1970s when it became possible to manipulate the genetic material of the crops. Manipulation of genes relies on the tools of genetic engineering which can cut DNA in specific places and join the broken pieces of DNA. Together, these tools are used to “cut and paste” DNA sequences from multiple sources resulting in recombinant DNA. This manipulated DNA can then be introduced into an organism by several methods. In plants, the methods to introduce DNA involves shooting the DNA into the plant cells using gene guns, electric pulses, or directly injecting the cells with DNA. Another common technique to introduce genes into plants involves using Agrobacterium tumefaciens, a common plant parasite, which inserts its genes into the plant host as a part of its infection cycle and could be thus used to introduce desirable foreign genes into plants.
The first genetically modified plant was an antibiotic resistant tobacco plant produced in 1983. The process of introducing a gene into another organism is complicated and is associated with a high risk of failure. Therefore, additional marker genes are used to enable faster screening of plants that have been successfully modified. These marker genes usually code for antibiotic resistance or herbicide tolerance. The plants that have integrated the new DNA can withstand treatment with antibiotics or herbicides, whereas the plants without this DNA perish. However, incorporating such genes can have other adverse effects as discussed below.
Following this, there were several GM crops that were developed including canola with a modified oil composition, virus-resistant squash, and Bt crops (Bt cotton, Bt maize and Bt potato). Bt crops were all developed in 1995-1996 and became popular because they reduced the need for chemical pesticides. The crops contained genes from the organism Bacillus thuringiensis or Bt, which produces crystal proteins that are insecticidal. The mechanism of death is quite gruesome: the protein crystals dissolve in the insect gut leading to paralysis of the digestive tract. The insects feeding on Bt crops then die of starvation. In 2000, golden rice was created to supplement the diets of Asian countries with vitamin A, whose deficiency kills around 670,000 children under the age of five, every year. The modified rice was improved in 2005 to produce 23 times more beta-carotene, the precursor of vitamin A, compared to the original golden rice. However, the rice has still not made the transition from field to market. Currently, about 28 countries produce GM foods, with the U.S. being the leading producer.
Humans have a long history of genetically manipulating animals through domestication. Dogs were domesticated at least 15,000 years ago to serve as companions. Sheep, goats, and cattle were domesticated for consumption, horses, oxen, and camel were used for transportation, and silkworms and honey bees for their commercial value. Domestication lead to the development of traits that made the domesticated animals completely distinct from their wild counterparts.
The process of modifying animals using genetic engineering has only recently shown results. In 2002, researchers at Caltech created glow-in-the-dark mice by using a jellyfish gene that codes for green fluorescence. In the same year, researchers successfully modified mammalian cells to secrete protein filaments that constitute spider silk. The resulting silk is flexible, lightweight, and possesses strength and toughness. Scientists were also able to introduce the genes required for synthesizing spider silk into goats so that they would secrete silk proteins into their milk, making it easier to harvest.
In 2015, AquAdvantage salmon became the first GM animal to be approved for consumption. This salmon has accelerated growth rates compared to wild type salmon and can breed all year round instead of only during spring and summer. Currently, researchers are working to use genetic engineering as a tool to reduce global warming by producing cows that are less and therefore have lower emissions of methane, a potent greenhouse gas.
The oldest argument is that the science is not understood well enough or properly regulated. Other concerns include the risk of cancer and the unknown long term effects. GM food is known as “Frankenfood” and considered unnatural, contaminating the environment and causing an increase in herbicide. Although some of these concerns are valid, the majority of them are completely misplaced.
Genetic modification has been crucial in understanding how biological systems work. Without this technique, it would be impossible to synthesize products such as vitamin B2, alcohol and mono-sodium glutamate (MSG) on an industrial scale. Each of these processes are dependent on micro-organisms that have been modified to pump out these products. It is untrue that manipulating DNA leads to the formation of Frankenfood, for example introducing anti-freeze genes from Arctic fish into tomatoes does not lead to the production of tomatoes with fish tails. DNA is simply a language and can be manipulated to encode the required message without leading to aberrant results.
Many GM crops have been synthesized to be resistant to pesticides – a useful trait that should lead to the elimination of weeds without compromising the crops. However, the potential problem that might arise here is that spraying the weeds with pesticides could eventually lead to formation of resistant weeds. In order to counter this problem, the EPA and the WHO investigate, monitor, and regulate the use of pesticides with multi-pronged approaches. The pesticides are evaluated every 15 years to ensure their safety, farmers are warned against using higher pesticide doses, and synthetic pesticides are being developed that are highly specific against a particular pest.
It is true that the long term effects of these foods on humans are unknown. However, the long term studies done on rats, have shown them to be an acceptable model for humans and indicate that these foods do not cause cancer, affect health, vitality of these animals and of future generations, another concern voiced by the anti-GM advocates.
Another concern related to the use of GM foods is that they make us more vulnerable to allergens. One of the arguments that anti-GM advocates conventionally use, is that GM crops may produce new allergens. As described above, the only way to create GM crops is to purposefully manipulate the genes. This means that there needs to be a malicious intent to introduce genes encoding allergens. Second argument they use is that the protein crystals in Bt corn can cause allergic reactions. This is again untrue because proteins are mainly expressed in leaves and not in cobs.
The current scientific consensus is that GM foods are as safe as conventional foods. There are several regulatory agencies in countries across the world that constantly monitor the effects of GM crops on the environment and human health. It is unfair to completely dismiss a new technology based on unfounded fears of the unknown. Although it is impossible to completely eliminate all the risks associated with GM crops, I believe that the benefits of these crops likely outweigh any potential risks.
Author
Ananya Sen is currently a Ph.D student in Microbiology at University of Illinois at Urbana-Champaign. When she’s not studying oxidative stress, she is busy pursuing her passion for scientific writing. Currently she contributes articles to ASM, ScienceSeeker, and her own blog where she discusses the history of various scientific processes. She is an ardent reader and will happily discuss anything from Jane Austen to Gillian Flynn. Her graduation goals include covering all the national parks in the U.S. with her sidekick Oscar, a Schnauzer/Pomeranian mix.
Editors
Paurvi Shinde d
id her Ph.D. in Immunology from University of Connecticut Health. She currently works as a Post Doc Fellow at Fred Hutchinson Cancer Research Center, where she studies the role of immune cells in providing protection against HSV-2 infection. Apart from research, she loves editing articles, listening to podcasts, dancing and hiking in the beautiful Pacific Northwest. Follow her on Linkedin.
Roopsha Sengupta did her Ph.D. from Institute of Molecular Pathology, Vienna and Postdoctoral research at University of Cambridge UK, specializing in the field of Epigenetics. Besides science and words, she enjoys spending time with children, doodling, and singing.
Illustrator
Bhrugu Yagnik is a post-doc at Emory Vaccine Centre, Yerkes National Primate Research Centre, Emory University, Atlanta, GA and works on the development of a HIV/AIDS vaccine. His doctoral research focused on the development of vaccines against Shigella using food grade Lactococcus lactis as an antigen delivery vehicle. Bhrugu has many awards to his credit which includes Lady Tata Memorial Fellowship Award 2014 (India), 2016 International Society Vaccine (ISV) Congress Award (Boston, MA), Dr. G. P. Talwar Young Scientist Award 2017 (Indian Immunology Society, India) and AIDS Vaccine 200 (AV200) Fellowship Award (Atlanta, GA). He is passionate about communicating the science in creative ways. In his free time, Bhrugu indulges himself in spirituality where he attempts to bring an amalgamation of science and spirituality. Connect with him on LinkedIn or ResearchGate.
Blog Design: Paurvi Shinde
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