In the past two years or so, genetic engineering has entered the spotlight of the common cultural discourse. As a result, there has been an explosion of bad information, intentional misinformation, ignorance, and by consequence, fear. As a geneticist by training, this bothers me a great deal. I’ve posted about it before, and I’m sure I’ll do so again, but for my first “Science” post I’d like to do it now.
“GE” versus “GMO”
Before I get to the meat of the matter, we need to talk terminology for a bit. You’ll find that throughout this post and elsewhere, I tend to use “GE” or “Genetically Engineered” rather than “GMO” or “Genetically Modified Organism.” That’s not an attempt to distract or obfuscate; much the opposite, in fact. I use the former term rather than the latter because it is more accurate.
Ever since the beginning of agriculture in Mesopotamia about 10,000 years ago, we’ve been modifying DNA. Ever since we intentionally domesticated the dog, we’ve been modifying DNA. To make those changes, to make fruits get bigger or bodies get smaller, we bred organisms with traits we wanted with other organisms that also had traits we wanted – selective breeding. Another term for this is evolution by artificial selection. In so doing, for instance, we increased the amount of DNA in the strawberry up to 32-fold, so that commercial domesticated strawberries have up to 32 times as much DNA per cell as the wild strawberry, through the duplication of whole chromosomes. In dogs, the changes are more subtle but no less substantial. Genes, and more often regulatory elements – which are stretches of DNA that do nothing other than tell cellular machinery when, where, and how much of a certain protein to make – were changed out, the end result is a creature tailor made for hunting, herding, guarding, or whatever else we desired. The short version of the story is that we have been modifying DNA for a very, very long time.
Engineering is a more intentional, more directed process. When we engineer items, we build things like circuits or rockets or skyscrapers, from nuts and bolts to blueprints and floor plans. We’ve understood the basic structure and importance of DNA for generation or three. Dr. James Watson and Dr. Francis Crick published their landmark paper on the structure of DNA in 1953, and in 1972 we made the first intentional change to living DNA by inserting a gene from one bacterium into another bacterium, proving that it could be done and was stable even after several generations. The process has gotten a whole lot easier and a whole lot more robust since then, but the fundamentals remain largely the same.
Given that it is the latter process that most people are referring to when they use the term “GMO” and not the former process, I choose to use “GE” or “Genetically Engineered” when talking about that, and you should too. If you want to be taken seriously when speaking on scientific issues, start by sounding like you know what you’re talking about.
The Story of Genetic Engineering
It is useful to start our tale with a historical perspective, an exposition on just what genetic engineering is, how it works, and how it came about. Like I mentioned earlier, in 1953 Watson & Crick published their paper on the structure of DNA. That ended one era of scientific inquiry, and started another. Up to that point, the main thrust of research in that field had mostly been directed to determine what the “heritable material” was – or, what was it that was passed on from parent to child that made the latter look and act mostly like a blend of the former (separately and much earlier, scientists [namely Gregor Mendel] had determined how inheritance worked in general, and gave us a basic vocabulary for genetics, but I’m going to ignore that for the moment). They determined that the heritable material was DNA, and then started to work at discovering just what DNA was and how it worked. Through a series of experiments they uncovered the following facts:
- DNA was a polymer, a molecule made up of building blocks. Those building blocks were Adenine, Cytosine, Guanine, and Thymine. These four molecules were acidic, and were found mostly in the nucleus of cells, so they were called nucleic acids.
- In any given DNA molecule, there was always exactly as much Adenine as Thymine, and exactly as much Cytosine as Guanine. That ratio was not true for any other pair of nucleic acids.
- DNA did not come in single molecules, but in pairs. This pairing was joined together by a kind of bond called a hydrogen bond that could break and reform rather easily.
- DNA was a molecule that, when bonded in stable pairs as happens in regular cells, looked kind of like a twisted ladder. This is called a double helix.
These were all really cool factoids on their own, but until Watson & Crick (and Franklin and Wilkins) synthesized them into a coherent model by adding a few bits of their own data and spending many hours essentially playing with Legos, they were all mildly cool, but not really useful for anything. Then, they published their paper in 1953, and the whole world of molecular biology was set alight with new purpose, and a new era of research began.
After Watson & Crick, the main thrust of genetic and molecular biological research shifted from what the heritable principle was and how it worked, to how we could use it to best benefit society. One of the most important things to happen after that point was a very fortuitous cup of coffee between two scientists – Dr. Herbert Boyer and Dr. Stanley Cohen. They discovered that though they were working on two different topics, their work was very complementary to one another. One was working on plasmids, which were special molecules – chromosomes – that sometimes happened in bacteria, researching how they worked and how they might be made. The other was working on a peculiar defense mechanism in bacteria, called a restriction enzyme. These were proteins that were programmed to cut any DNA that had a particular sequence in it. The sequence was usually uncommon enough that it never occurred in the bacterium’s own DNA, but it did occur in the DNA of other bacteria or viruses that the bacterium was protecting itself against. So, if the bacterium ever encountered any of those bacteria/viruses, the restriction enzymes would cut up the DNA of the target and kill them. But, importantly, the ends of the pieces of DNA that the enzymes cut were “sticky” to other ends of other pieces of DNA cut by the same enzyme. Upon realizing this, a light bulb went off somewhere. If two pieces of DNA – one being the place you wanted to stick a piece of DNA, the other being the piece of DNA you wanted to stick there – were both cut with the same restriction enzyme, you could use one piece of cut DNA like a bandage on the other, and would at once repair the damage and insert the DNA you wanted into the target you wanted.
At first, this was only tried with the DNA of bacteria. Eventually, scientists found that you could mix the DNA of literally anything with anything, at least most of the time, and get the gene you wanted inserted into the DNA you wanted if you did it just right. Out of this discovery was born a whole industry, and hundreds of scientists dedicated their lives to studying this further. I’m one of them, though I must admit my own contributions have been small and unimportant by comparison.
Around this time, people figured out that there was a great deal of money to be made in this. What began as a line of research meant for the public good, to do things like cure cystic fibrosis and sickle-cell anemia, Alzheimer’s and cancer, world hunger and environmental ruin, was turned into an engine of profit for companies like Dow and Monsanto.
In the next page of this history, I’ll cover current applications of genetic engineering along with descriptions and a few details on each. That will lead us into part 3, where I will talk about the current controversy over GE crops.
Continued in part 2…