What is a GMO… And why are they in my food?

Posted on February 26, 2011


In Michigan, come March and April, you may find yourself bombarded with displays of seeds and gardening supplies at pretty much every store around. Spring is the time to start thinking about what to plant in that lovely summer escape known simply as “Your Garden”.  But later as all those farms and gardens are starting to show off their stuff, I find myself wondering, where did all those little seeds come from in the first place? Maybe you saved last year’s seeds, bought them at the supermarket, ordered from a catalog, or purchased a special Organic or Heirloom variety. Maybe you bought starter plants and didn’t use seeds at all. Or maybe you prefer to purchase produce from a farmer, Co-op, or grocery store. No matter where they came from, it’s important to know the story behind your vegetables.

If you’re interested in where your food comes from you’ve probably heard the term GMO (Genetically Modified Organism), GM (Genetically Modified), or GE (Genetically Engineered) before. What you may not know is exactly how the process differs from traditional breeding and hybridization techniques.

Traditional hybrids are created by crossbreeding compatible organisms to pass on desired traits. In other words, one plant’s pollen fertilizes another’s seeds, and the offspring shares traits from both parents. While this is a simple natural process it is also a long one. (And it is limited to plants that are already genetically compatible.) It can take many generations of crossbreeding to create a stable and reproducible hybrid. In our “agribusiness” culture not everyone is that patient. This is where GMOs come into the picture.

GMOs are produced by artificially inserting new DNA into an existing organism. Because the DNA is inserted directly it is easier and faster to alter the desired trait. There are two separate types of GMOs, transgenic and cisgenic. Cisgenic organisms only contain DNA from the same species, while they are still genetically engineered they are similar to traditional hybrids in this respect. Transgenic GMOs involve the addition of DNA from completely different species of plants, animals, or sometimes both.

Now these transgenic GMOs present a unique problem. How exactly do you get a tomato seed to accept the DNA of a fish? You have to break in; and nothing is better at breaking into cells than bacteria and viruses. So to get new DNA into a cell geneticists attach a little piece of bacteria or virus. This helps the new DNA to break through the cell’s natural defenses and carry the information into the nucleus. (You can also shoot the DNA into the cell with a Gene Gun, but this technique is not as effective so it is used less often.) The nucleus is where all the genetic information needed to make a new tomato, potato, or fish is stored. So now you have a bit of virus or bacteria hiding inside your cell.

Of course, this doesn’t always work exactly like it is supposed to, so there needs to be a way of checking where that DNA went within the cell, and whether or not it is active. Little bits of DNA can be hard to spot on their own, but this problem can be addressed by adding a marker to the inserted DNA. The marker of choice is usually a gene that confers resistance to an antibiotic or herbicide. Then the cells are incubated along with the antibiotic or herbicide. Only those that contain the new genes and resistant marker will grow, making this an easy way to single out successful gene transfers. Now you have bits of virus or bacteria in a cell that is resistant to an antibiotic or herbicide.

What effect could these GMOs have on our health and our food supply? That’s the question I’ll be addressing next time. Some of the most commonly voiced concerns include the possibility of increasing antibiotic resistance, virus fragments that can recombine to form new contagions, and unique or increasingly potent allergens. This is an immensely complex issue. (For example: Is a vegetable containing animal DNA still vegetarian?) While I have researched this topic to the best of my abilities there is no substitute for firsthand knowledge. If you want to investigate for yourself, here are some good sources of information:


I originally wrote this series of articles for the GreenTree Co-op Newsletter, but I thought they were interesting enough to merit reprinting here.