Growing up, I was surrounded by fields of corn that often stretched as far as the eye can see. I grew up on a farm in southern Indiana, so that should not be surprising. My father, uncle, and cousin still farm, growing two of our nation’s staple commodity crops: corn and soybeans. In fact, my very first job was detasseling corn. If you are not familiar with the process, suffice it to say that the job provides excellent motivation for one to pursue academic success and seek out a job that involves air conditioning. Anyhow, corn is just one of many crops that play a central role in the ongoing discussion about genetically modified organisms (GMOs) that is taking place around the world. Did you know that 90% of the corn grown in the United States last year was genetically engineered? According to the USDA, that number has been steadily growing for more than a decade.
So what exactly does GMO mean, and how does it relate to genetic engineering? The phrase has become a bit of a buzzword that, for many, carries some very negative connotations. Although it is commonly used to refer to crops or food, the phrase is actually very general since not all modified organisms are used in food production. To say that something has been “genetically modified” would indicate that it has been subjected to genetic engineering, meaning that its genome (in other words, the sum total of its genetic material) has been altered in some fashion. This is different from saying that the organism is “transgenic”, which would indicate that foreign genetic material has been introduced into the organism’s genome. In other words, if something is transgenic, then it has been genetically modified, but if something is genetically modified, it is not necessarily transgenic. Make sense?
Humans have a long history of making genetic modifications to plants and animals, though we like to call it agriculture, animal husbandry, domestication, or more recently scientific research. Corn as we know it today was not found growing in the wild, but rather it has been modified by centuries of selective breeding to produce the tall stalk and large kernels that have become so familiar to us (see image below). Selective breeding essentially speeds up the process of natural selection by propagating only those organisms with the desired traits. This could mean breeding cattle to produce more meat or milk, breeding smaller or faster dogs, breeding plants that bear more fruit or have greater resistance to insects, and so forth.
Selective breeding imposes artificial selection upon a particular organism in order to isolate or combine desirable traits within a species, or to take advantage of valuable mutations that occur, or even create conditions where such mutations become more likely. Of course, sometimes our actions apply selection pressures that result in undesirable outcomes as well, as is the case with the development of antimicrobial resistance in a wide range of pathogens due to the overuse of antimicrobial drugs. Humans are also subject to such selection pressure, as exemplified by the ability of a large portion of the population to process lactose (consume dairy products) beyond infancy, thanks to our animal husbandry practices. On the whole, I think it is fairly safe to say that mankind has benefited greatly from the ability to modify organisms to better suit our needs. One might even argue that it is one of the driving factors that has allowed humans to progress from sharpened sticks to nuclear warheads. Your call on whether or not that was such a good thing.
So the leap from natural selection to artificial selection greatly sped up the rate at which we could modify organisms, but the process is rather limited. In essence, you have to work with what you have available. You might want one animal or plant to have the same trait as another, but if you are not able to breed them or graft them together, then you are unlikely to succeed at transferring that trait. With improved understanding of genetics and molecular biology, however, we have overcome these constraints. We continue to learn how to identify the molecular origins of these traits and decipher how they are regulated within an organism. It is even possible to transfer these mechanisms from one organism to another, and that is what we call genetic engineering. This brings us back to the idea of transgenic organisms, which is what people are really concerned about when they throw around the term “GMO” with such disdain.
This is an issue that I try to keep track of, not only as a result of my agricultural upbringing, but also because of my interest in molecular biology and my concern for the future of humanity. Like so many things, the issue itself can be rather polarizing, but that does not mean that one side is right and the other is wrong. In this post I began exploring the topic of genetic modifications to organisms in order to lay the groundwork for my next post, in which I intend to begin exploring in a little more detail the controversy surrounding GMOs.
Thanks for reading!