GMOs Demystified- Part 1: Basics of Genetic Engineering

Rural System, above all else, is an approach to land management that emphasizes reasonableness in making management decisions. “How much profit can be made?” is balanced with “How long will profit be made?” “What’s good for humans?” is balanced with “What is good for the ecosystem?” All management decisions are made according to the most recent scientific knowledge on the topic.

The debate over genetically modified food has been extensive and multi-faceted. Like many sensationalized issues, it can be difficult to sort out truth from bias. This series of posts before you is a guide to GMOs based on available science rather than uninformed opinion. Our first question: how is genetic engineering done?

Genetic engineering is now a simple procedure used to produce many different genetically modified organisms.

1. Genetic engineering invariably involves recombinant DNA:

Bacteria and Archaea have enzymes to defend against viruses called restriction enzymes. These enzymes are designed to recognize and cut apart foreign DNA, and so prevent a virus from replicating inside the cell. Every restriction enzyme cuts DNA at a unique site, and it does a rather zig-zagged job of it, leaving exposed strands of single DNA called sticky ends. These sticky ends are only attracted to other sticky ends cut by the same restriction enzyme. So, if you’re a genetic engineer and you want to take DNA of two different organisms and splice them together, you must carefully choose a restriction enzyme and use it to cut the DNA of both organisms so that it might recombine to form hybrid strands. You have now made recombinant DNA.

2. But how is recombinant DNA used? There are several methods of introducing the engineered DNA into a cell, which could be a bacterium or the gametes of, say, corn.

  • Plasmids are a common vector for transforming target cells with foreign DNA. Bacteria often have little mini circles of DNA called plasmids in addition to their own circular genome. Plasmids are often self-replicating (they code for enzymes that will replicate them) and can be passed from bacteria to bacteria in the bacterial equivalent of sex. These little circles are indispensable to genetic engineering. You can cut out the human gene for insulin production with a restriction enzyme, cut a plasmid with the same enzyme, and recombine the human gene into the plasmid. If you then put that plasmid into a bacteria cell and let the bacteria replicate, as they do rapidly, then you will have huge cultures of bacteria that produce human insulin. This was the first commercial product produced by genetic engineering in 1982 and it has since saved millions of lives. The scientific community has not found any health ramifications for the use of this genetically modified product.
  • Microinjection, as you might guess, involves injecting the DNA directly into the nucleus of the target cell.
  • Biolistics, etymologically related to ballistics, involves blasting host cells with microprojectiles of gold or tungsten, coated with DNA, at high speeds. The projectiles deliver the DNA into the nucleus of the cells, where it can then be taken up into the cell’s genome.

It is important to note here that most genetic engineering is done to add a single trait to an existing organism, such as a tomato. This means only a relatively small amount of DNA is being added and the proteins to be produced form the DNA template are known. The similarity of the proteins to known allergens will also be known, so risk of negative health effects can be evaluated even before testing begins to determine that the product is safe for consumption.

There is plenty of information on the GMO controversy, but it is much easier to navigate with a guide. Coming up next: discover how GM products might affect your health.

Read the whole series, or pick a topic that interests you:

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About Laurel Sindewald

Laurel is an alumna of Warren Wilson College with a BS in Conservation Biology and a BA in Philosophy. She is a writer for Rural System, Inc.


  1. Risa Pesapane says:

    I think one of the most interesting debates in GMO is how “genetically modified” is defined. Technically cross-breeding of plants is genetic modification. Much like the breeding of dogs for certain characteristics, humans have been genetically modifying plants for specific traits which may not have occurred naturally. This is also a concern for the cross-breeding of these hybrids with native or natural strains. I think most people attribute “genetic modification” to what is achieved by adding DNA from other organisms (non-plants) to plants……but it is also important to recognize the extent of genetic modification and what we mean when we demand changes or labeling of products.

    • Laurel Sindewald says:

      Yes! And one thing I found personally interesting is that cross-breeding plants can be a much riskier form of genetic modification, because the interactions between all the different genes are unknown. You could end up breeding for a trait for pest-resistance and find out later that the plant is so toxic it’s harmful to humans too. Or maybe the crop will produce a new allergen. There are so many genes involved, likely with complicated linkage patterns, that the effects are highly unpredictable. In a way, the more direct form of genetic modification is more precise and therefore less risky. But then, health risks are only part of the picture…

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