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18 February 2014

What You Probably Didn't Know About GM

Genetic Modification*. That is what GM stands for, and that fact alone is what many of you probably already did not know. Even if you did know that, chances are you don't know what it means. This article is not going to go into great detail, but instead will focus on one misunderstood detail that, outside of academia and a lab, seems to be either sadly absent, or grossly misrepresented, right from the start of any conversation on the topic: The correlation between Artificial Selection and Genetic Modification. Genetic Modification does not mean, "performed in a lab, à la Frankenstein's Monster". It simply means what it says. Genes are modified.

This can be done in any number of ways, one of which is Artificial Selection. What is Artificial Selection? Well, it too is just what it says. Most of you, hopefully, are familiar with the term "selective breeding" - at the very least, where it relates to dog breeds. In short, that is where humans have chosen specific phenotypes, physically observable traits (e.g., large ears), that appear in one kind of dog and other traits (e.g., short legs) that appear in another kind of dog, and have the two mate in order to introduce all of the desired traits into the next generation. If two dogs of a litter of six have both long ears and short legs, only those two are chosen to mate with other dogs that also have both long ears and short legs. What they are doing here is choosing the traits that are expressed from certain genes to manipulate, or modify, what genes carry on. These dog breeders have just performed genetic modification. Similarly, when this is done in a lab, on a microscopic level, scientists are selecting specific genes from one organism to be expressed in another. Natural Selection would simply be when this happens without human assistance. For a fun and commonly used example of one way this can occur, looking at Californian salamanders, you can click HERE.

Here, the dogs represent the phenotypes (traits/characteristics) and the letters (The Ls and Ss) represent the alleles. If the dogs physically mate as shown,  then they carry these alleles, and the result is dogs with long fur. If we look at these same genes in the lab, and physically move the alleles along the same path, and then use those genes to form puppy embryos, the result is dogs with long fur. In both cases, the genes were modified as alleles were moved from one set of genes to another set of genes. Also, in both cases, the same materials, the same genes, are being used. There are no Frankenstein Monsters here, only shaggy puppies that will require lots of brushing. Lint brush not included.

I do want to note that saying that all of the last group of dogs can "only" have long fur is not accurate; there can always be mutations, dormant recessive genes, and so on.

You may have seen this graphic, to the right, used as a meme on Facebook, Twitter, Tumblr, et cetera, in the context of being snarky towards people who count themselves as part of an anti-GM movement. In another context, however, it can ring true. In fact, it could easily have come from a professor's presentation for a BIO 101 class. On the left is an image of what is likely a teosinte, one of the forerunners (more details HERE) of what we now call corn. On the right, is an image of corn, or maize, as we know it today, descended from generations of crossbreeding (more details HERE). Now, the plant on the right could have just as easily been the result of generations of crossbreeding on a farm (Artificial Selection) or in the wild (Natural Selection) as it could have been the result of choosing and splicing the same exact genes in a lab (Artificial Selection). The difference between doing it in the lab, is that you can do it in far fewer generations because you can literally see the specific genes and grab them, so there is little guesswork on how to get them to where they are wanted. All we know for certain about the image on the right is that it is the result of some form of genetic modification.

Just as Natural Selection is merely one of several ways in which evolution can occur, modifying genotypes in a laboratory, for the purpose of expressing desired phenotypes for a plant, is just one of many kinds of Artificial Selection, with results being no different than working directly with the traits in a field. In other words, not all GM is done by selective breeding, but all selective breeding is GM.

An analogous image could be made using cake batter (stay with me here). On the left, would be an image of two eggs, a cup of water, and a box of cake mix (not yet modified). On the right, would be cake batter in a bowl (modified). The heading would be, "A visual guide to identifying cake mix that's ready to bake". Under the left image, you would see, "Not ready to bake". On the right, would be, "Ready to bake". What we do not know is if the batter was mixed with a fork, or an electric hand mixer, using the same ingredients, "ingredients" being analogous to genes. What we do know, regardless of what tool was used to mix those ingredients, is that I am about to eat cake.

*Note: This is also known as Genetic Engineering (GE).

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