by Julia Budassi
Genetically modified organisms (GMOs) are living things that have had a change engineered into their genome, or DNA. DNA is the molecule that describes the specific traits and characteristics of an organism; things like what an organism’s eye color or blood type is, how good it may be at digesting lactose, or how susceptible it may be to certain diseases. The information contained in DNA is decoded within an organism’s cells to produce its observable characteristics. The genome, the entirety of an organism’s DNA, is ultimately what distinguishes one organism from another. For example, the difference between humans and corn is a difference in the number, identity, and expression of the genes within their genomes. If you think of the genome as a cook book written in the language of DNA, the genes are single recipes for certain traits. The genome of a GMO has certain recipes that are changed artificially, meaning that recipes within the book are added, removed, or altered.
Graphic: Mark Mace
When GMOs are discussed in the news, genetically modified crops are most often the topic of the discussion. With this understanding of what a GMO is, you may be wondering why anyone would want to change the cookbooks of our crops to begin with. There are many benefits to genetically modifying crops, including improved shelf life, nutritional content, flavor, color, texture, and “farmability”. Improving shelf life is becoming increasingly important because of the global trade of crops, which requires produce to travel long distances before it reaches its consumer. The nutritional quality and farmability of plants is also crucial for nourishing a growing global population in economic positions spanning from third world to first world countries. While changes to crops that produce these effects are economically necessary, the question that we should be asking ourselves is the following: are they safe for humans to eat and for the environment to sustain? If there are risks involved with crops containing some altered genetic recipes, are the modifications truly yielding beneficial results that outweigh these risks? These big questions about GM crop growth show that the matter is of significant importance to public welfare and the agricultural industry. At the same time, trying to answer the questions reveals that there is an intimidating volume of information on the subject accessible to people. The best way to sift through all the literature and develop a well-informed opinion on the issue is to truly understand the science behind GMOs.
Scientists use plasmids for genetic modification because plasmids are naturally occurring molecules meant for the relatively simple exchange of genetic information. If a bacterium’s genome, or its cook book, lacks a gene, or recipe, scientists can use plasmids to send over the new recipe and have it added to the book. Plasmids with genes inserted into them are called recombinant plasmids. The recombinant plasmid is like a Trojan horse since the cell takes it up not knowing that it contains something foreign to it. The foreign content, however, does not ultimately attack the cell but is incorporated into its regular activities. The bacterium doesn’t mind cooking up whatever its new recipe calls for, it doesn’t know any better.
Once the plasmid is inside the plant cell, getting the recipe added into the cookbook is more complicated than it is in bacterial cells. As a result, recombinant plasmids are made not only by adding the gene scientists want to see the plant express, but also by adding a number of other DNA sequences that make the plasmid more compatible with the plant genome. There is a compatibility problem because plasmids, naturally occurring in bacterial cells, are written in the style of bacterial cookbooks. While plant cookbooks are written in the same language as bacterial cook books, the language of DNA, the writing style is a bit different. It would be like giving an American chef who is used to tablespoons and ounces an English chef’s recipe written in grams and milliliters. It is all the same language, but there is a conversion issue that would look suspicious to the plant cell chef resulting in the denial of the recipe’s addition to the book. The extra sequences inserted into the recombinant plasmid used for transforming plant cells are like a conversion chart that will make the new recipe compatible with the plant cookbook, and therefore an acceptable addition to the book.
Aphids Photo Credit: Alvesgaspar & Corn Photo Credit: IRRI Images & Graphic: Mark Mace
The transformation process occurs in plant cells that scientists grow in petri dishes. The cells that successfully incorporate the recombinant plasmids into their genomes are identified, isolated, and grown into whole plants. The seeds of these plants will contain the recombinant DNA. When those seeds are grown in the soil, as opposed to starting as cells in petri dishes, they will produce plants that also contain the recombinant DNA, and can grow to create a family line of plants with the new gene.
When addressing crops with new genes, the question of whether the new genes change how safe the crops are is a complicated and crucial one. The most important issue to address is human health. The comparison of GM crops and their non-GM counterparts is in their chemical compositions and amounts of different molecules like proteins, carbohydrates, and lipids, the different molecules our bodies obtain from food for nutrition, as well as other nutrition related compounds like minerals. Modified corn and canola seeds, for example, contain amounts of certain classes of nutritional molecules that vary from their non-modified counterparts. Sometimes molecules were found in greater quantities in the modified crops, sometimes in lesser quantities, others were found not to have changed. The conclusions of these studies were simply that there were chemical differences between some modified crops and their non-modified counterparts, but not that the differences resulted in any sort of toxicity or danger to human health upon consumption. Furthermore, a 2008 article on GM crop safety reported that in the fifteen years of GM crop consumption prior to the article’s publishing, there have been no reported ill effects or successful legal cases related to the effects of GM crops on human health.
Environmental safety is another consideration that cannot be overlooked when discussing agricultural issues. A common genetic modification made to crops is the addition of a gene which produces a molecule that targets and kills specific pests. Adding this gene to crops allows the crops to protect themselves, eliminating farmers’ need to use chemical pesticides. Pesticides are used to kill specific pests, but the problem with any sort of pesticide, whether it be chemical pesticides or the molecule that comes from the gene used to modify the crops, is the depletion of biodiversity due to some degree indiscriminate, as opposed to targeted, killing of wildlife. A diverse population of insects and soil bacteria is important to the health of the environment because of the different roles they play in the food chain and in natural cycling of organic and inorganic resources. To assess GM crops’ effect on the environment, a study was conducted measuring the size of the population of organisms in crop fields that are not the targets of the plants’ genetically produced pesticides. These non-target populations were monitored in fields where GM crops were grown, in fields where chemical pesticides were used on non-GM crops, and in fields where no pesticides were used at all and the crops grown were also non-GM. This particular study concluded that GM crops are safer than using chemical pesticides to protect crop growth, but more harmful to the environment than not protecting crop growth at all.
Graphics: Melissa Hoffman & Mark Mace, See Photo credits in footnote*
Another environmental concern is the risk of crossbreeding between the genetically modified crops and wild relatives. This type of crossbreeding may develop super weeds that could, as a result of overgrowth, impact the soil ecosystem; a problem which currently exists and has been reported on in the past. While GM crops are safer to the soil ecosystem than chemical pesticides, a weed which does not have its growth controlled and confined like crops do could have a greater impact on non-target species than the crops containing the same foreign gene. With this in mind, there are a number of strategies implemented when growing GM crops to prevent gene flow to the wider environment. These include breeding the crops in isolation and growing seeds in isolated greenhouses or in fields that do not grow any weeds or crops related to the GM plant, eliminating the chance of crossbreeding.
While there is some environmental risk related to the cultivation of GM crops, there have been studies conducted that demonstrate the benefits reaped by growing these crops. The implications of these results are not trivial; increased crop yield could be extremely helpful for developing countries both in the way of food for the population and economic stimulation from selling the crops. On top of that, decreased use of pesticides is positive for both the health of the people and the environment. Countries with people who cannot afford much food other than the staple crop of the region could benefit from modifications that improve certain nutritional aspects of the crop by getting a more complete diet from the one food item they can afford.
GMOs are a scientific achievement that has been applied to modern agriculture with the goal of improving crop quality and yield. While GM crops are known to be chemically different from their non-GM counterparts, there has been no documented evidence of their danger to human health. There are serious environmental risks associated with the cultivation of GM crops, but with tight control, they are an effective method of increasing crop quality and yield and are less harmful to the environment than other methods of improved crop yield like the application of chemical pesticides.
Issue 1, October 2015
Photo Credit: United Soybean Board, Veganbaking.net, Pingpongwill, Uwe Hermann, flickr users nociveglia Rosana-Prada Kimberly-Vardeman geishabot