This is not an article about the pros and cons of genetically modified organisms. I am not arguing for them or against them. Instead, the goal of this article is to help you learn some of the basic science involved, to make it easier for you to fact check articles on this topic.
What is a GMO?
While I will be using the term "GMO" in this article, it is important to understand that GMO is a marketing term, not a scientific one. GMO stands for Genetically Modified Organism. These are living things which have had their genetic material changed in order to change something about the organism. The word “organism” includes all living things, so a GMO may be a plant, animal, bacteria, fungus, etc.
While there are many ways to genetically modify organisms, from selective breeding to using radiation or chemicals to increase mutations, most news articles on GMOs are referring to transgenic and cisgenic organisms. Transgenic organisms have had genes from other organisms inserted into their DNA. Cisgenic organisms have had a gene removed, altered, and then reinserted. The term "GMO" does not include organisms that have had their genetic information changed by exposure to radiation or mutagenic chemicals. It also does not include organisms that have had their genetic information altered by CRISPR gene editing.
DNA and genes
DNA stands for Deoxyribonucleic acid, a large molecule that is the genetic blueprint to tell each cell in your body what to do and when to do it. Each molecule of DNA is made up of a long chain of genes.
OK, so what are genes? A gene is a set of instructions that let a cell make protein molecules. Different genes make different proteins.
Proteins are complex molecules that do many different things. Some proteins are enzymes, speeding up chemical reactions. Others are antibodies, protecting you from disease. The haemoglobin that lets your blood carry oxygen is a protein. So is the cartilage that holds your skeleton together. Proteins such as insulin control the chemistry of our bodies, while other proteins cause our muscles to move. All of your genetic traits, from eye color to blood type, are the result of different proteins produced by different genes.
How it works
Now that we have some basic information, it is time to dig into GMOs. Lets start with corn, since there are several common types of genetically altered corn. In 2009, scientists found that corn DNA is made up of about 32,000 genes. Selective breeding can be used to develop corn plants that are taller, have larger kernels, etc., but it is limited by the traits that are already there and random mutation. If you want a strain of corn that has a specific trait, wouldn't it help if you could add a gene for that trait?
A good example is SYN-EV176-9 (176) maize, sometimes known as bt corn. The bt stands for Bacillus thuringiensis, a naturally occurring soil bacteria that produces a protein called Cry1Ab. The CryaAb protein is toxic to some insects, including the European corn borer. By separating the gene for producing Cry1Ab from the DNA of this soil bacteria, and inserting it into the DNA of a strain of corn, you get corn plants that produce the Cry1Ab protein. This makes them toxic to European corn borers and other insect pests, letting farmers use less pesticides on their crops.
Now, lets look at MON-ØØ6Ø3-6 (NK603) corn, also known as Roundup Ready corn. This is corn that has had a gene from a soil bacteria called Agrobacterium tumefaciens inserted into its DNA. This gene produces the protein 5-enolpyruvlyshikimate-3-phosphate synthase. This is an enzyme that lets the plant tolerate levels of glyphosate (Roundup) that would normally kill the plant. One of the challenges of farming is trying to kill the weeds without also killing the crops. If crops have a much higher resistance to herbicides, it is much easier to kill the weeds.
Notice that these two genetically altered organisms had different genes from different organisms inserted into their DNA to produce different proteins with different results. The traits that they have in common are traits that came from the original corn.
Now lets make things even more different by looking at tomato line 1345-4. In this case, the 1-aminocyclopropane-1-carboxyllic acid (ACC) synthase gene is removed from the Tomato DNA. This gene produces proteins that produce ethylene gas, which controls ripening of the tomato. Part of the gene is removed, and then it is reinserted. This greatly reduces ethylene production. Ethylene causes tomatoes to ripen, so reducing the amount of ethylene causes the tomatoes to ripen slower, giving them a much longer shelf life at the grocery.
This "GMO" is even more different from our previous two. The type of plant is different. It has a different gene inserted to change the production of a different protein. Even the source of the gene is different. In this case, it is a modified gene from the same kind of plant, making it a cisgenic organism instead of a transgenic organism. Cisgenic organisms have had their DNA altered with genes from the same kind of plant.
Warning! GMOs are GMOs!
One of the most important things to know when you are fact checking this topic is that each "GMO" involves different genes and different proteins. Pretty much the only generic claim that can accurately be made about genetically modified organisms is that they are genetically modified organisms. Any article that claims that all GMOs cause allergies, kill butterflies, are toxic, are safe, are not nutritious, are more nutritious, etc. is misleading you with unscientific information. Each has to be evaluated independently, to see how it is different from the original organism.
Scientific articles will focus on a specific organism, not genetically modified organisms in general. If a scientific study found evidence of a problem with SYN-EV176-9 (176) maize, that would not indicate any problems with any other genetically modified organisms.
Let me start by saying that I am in favor of labeling genetically modified foods, but NOT for simple labeling them as "GMO foods". This is one of the biggest misunderstandings with the push to label GMO foods. Just labeling them as "GMO" tells you absolutely nothing about possible allergens or other potential problems. It tells you nothing about any issues found in scientific studies. Simply labeling a food as "GMO" is like labeling pharmaceuticals as "medicine", without telling you what kind of medicine, what it contains, or what it is used for.
To get any useful information by labeling GMO foods, each label should include information on each inserted gene in each crop. That way, if for some reason you were allergic to 5-enolpyruvlyshikimate-3-phosphate synthase, you would know to avoid foods containing MON-ØØ6Ø3-6 (NK603) maize, but unless you were also allergic to phosphinothricin-N-acetyltransferase, it would be perfectly fine for you to eat SYN-EV176-9 (176) maize.
Beware of Single Studies
Another important thing to keep in mind whenever you are fact checking science is that a single scientific study does not provide conclusive evidence. A study that produces interesting or unexpected results will be replicated with other scientists. If those replications produce the same conclusions, the idea gains acceptance. If replicated studies find different results, then the idea loses acceptance.
When you see a study quoted on a controversial subject, search for studies by other scientists on the same topic. If you find ten or fifteen other studies that produce the same results, that would be pretty strong evidence. On the other hand, if the replications found different results, it would be strong evidence against the original study.
Keep Fact Checking!
As you can probably see, the science of genetically modified organisms is not nearly as simple as most articles make it sound. I have limited myself to helping you fact check the science behind GMOs, but there are plenty of misconceptions and false claims that are based on political issues. You should fact check those too, and a good place to start is with my earlier fact checking series, I Saw It on the Internet.