What's the difference between genetic engineering and selective breeding?

Q. I just read your story on GMOs and organic crops; what's the difference between cross pollination/grafting/selective breeding that farmers have been doing for centuries and genetic modification?  Just curious, because it seems like farmers have been screwing with genes for a long time now. – Joe, NY

A. You’re right, Joe. Farmers have used selective breeding for ages to increase the robustness and output of their crops and to produce and encourage other desirable traits. But there are some pretty huge differences between the techniques they’ve traditionally used and the high-tech ones being implemented today on mega farms that produce GM corn, cotton, soy, and canola (the four crops largely converted to GM technology so far). Put it this way: If traditional selective breeding is like two people with two different sets of genes being paired up by a matchmaker who thinks they’ll have pretty, healthy kids together, then modern high-tech GM breeding is like Victor Frankenstein slicing ‘superior’ body parts out of fifteen different corpses and using them to sew together his powerful, yet frighteningly unpredictable, monster. 

Whoops. Did that sound slightly unscientific and/or possibly biased? Then don’t take it from me—take it from Craig Holdrege, director of The Nature Institute. He explains that the most critical difference between natural and GM breeding is that natural breeding crosses only organisms that are already closely related—two varieties of corn, for example—whereas, in contrast, GM breeding slaps together genes from up to 15 wildly different sources. Here’s how he explained the convoluted GM breeding process to me in an email:

To make a GM plant, scientists need to isolate DNA from different organisms—bacteria, viruses, plants, and sometimes animals (or humans if the target gene is a human gene). They then recombine these genes biochemically in the lab to make a "gene construct," which can consist of DNA from five to fifteen different sources. This gene construct is cloned in bacteria to make lots of copies, which are then isolated. Next, the copies are shot into embryonic plant tissue (microprojectile bombardment), or moved into plant tissue via a particular bacterium (Agrobacterium) that acts as a vector. After getting the construct copies into the embryonic plant tissue, whole plants are regenerated. Only a few plants out of many hundreds will turn out to grow normally and exhibit the desired trait—such as herbicide resistance.

Or take it from Joe Mendelson, director of the Center for Food Safety. Here’s how he put in it in an email: 

The difference is pretty large. In regular cross pollination, the species being crossed have to be related . . . basically respecting their common evolutionary origin. But with GMOs, you can take any gene from any species and splice it into a crop. So you get fish genes in tomatoes or the like.

And it’s not just cotton, corn, soy, and canola that are being genetically modified anymore—GM alfalfa and GM sugar beets are on the way. Many food safety activists are, like Holdrege and Mendelson, concerned about the effects these six major GM crops will have on ecosystems, on agricultural production, and on our bodies. All that aggressive lab work, they argue, has the potential to bring consequences we can’t anticipate. Genetic modification has certainly upped agricultural output, which is a plus when food prices are high and many parts of the world are experiencing or are at risk for famine. But because almost all of us eat GM foods and produce every day, you’re wise to ask tough questions about the relatively new and largely untested technology. 

-         Tobin Hack

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