Tuesday, September 25, 2012

G-M-Oh-Oh (Part 1)

GMOs have been in the news a lot lately, so I’d like to talk about what they are and how they impact our lives (hint: it’s a pretty big impact!). And because there’s so much to say, I’ll be dedicating 3 blog posts to this topic. I hope that you’ll share this information, folks, because, at the very least, it’s important to be informed about what you’re putting in your body.
GMO stands for Genetically Modified Organisms.  They are also called transgenic organisms, as well as Genetically Engineered Organisms( GEOs). Sound like something from a futuristic sci-fi movie? Well, it kind of is. Let’s take a look, shall we?

First, a bit of history. For centuries, humans have been using selective breeding of plants and animals to take advantage of naturally occurring genetic variations and pass desired traits on to the next generation of organisms. That’s the process that brought us man’s best friend. Yup, I’m talking about good ol’ Rover, your family dog. Our ancestors domesticated wolves and used them as helpers for hunting. Then they chose which individual wolves to mate with one another, based on characteristics (friendliness, tamability, etc.) that they wanted to pass on to the next generation. Eventually, through thousands of generations, wolves became dogs. And today, we have a multitude of different breeds for different purposes - some for hunting, some for herding, some for guarding, some as lap-dogs, others for nothing more than being just plain adorable. (There are currently debates about the ethics of selectively breeding animals, especially livestock, for traits like larger sizes and quicker maturation periods. More on this in a future post.)

Selective breeding hasn’t been limited to just animals. Plants, too, have been modified to serve a variety of human needs. If you want to see dozens of examples, just walk into any florist’s store. Every commercially available flower has been bred over generations to give us a gorgeous palette to choose from when decorating our homes, celebrating milestone events or even wooing a love interest.

While selective breeding makes use of naturally existing characteristics within a species, genetic modification is accomplished through applying biotechnology directly to the genes themselves.

Genetic material is the blueprint that exists inside the cells of living organisms and controls factors such as growth and development. Genes are beaded along tightly bundled strands of deoxyribonucleic acid (you might know it better as DNA), and they use chemical messages to instruct a given cell to perform its functions by making proteins or enzymes.

Scientists can introduce a foreign gene into a cell and prompt it to make new proteins or enzymes, so that the cell performs new functions. These foreign genes can be taken from and inserted into any animal, plant or micro-organism. It is now not only possible, but very easy, to mix the genes of say, a fish and a strawberry. Really! The resulting organism, in our example, the strawberry with the inserted fish gene, is referred to as ‘transgenic’.

Right about now, you might be wondering how the cells are coaxed to accept the new genetic material. There are a myriad of ways, and none of them involve dinner and a movie.

Hold on to your hats, here we go:

Bacterial Carriers
The Agrobacterium can infect plants, which makes it a great carrier for delivering DNA. It is put through a preparation process, genetically modified, then allowed to infect the target plant cells, so it can deliver the new gene into these cells. Basically, it’s like an undercover agent sent into a foreign country.

The selected DNA is attached to microscopic particles of gold or tungsten. Like firing a gun, these DNA-laden particles are shot into the target cells by a burst of gas under pressure. Imagine watering your lawn with a high-pressure hose, where the water actually penetrates the grass leaves.

Calcium phosphate precipitation
The selected DNA is exposed to calcium phosphate. This mixture creates tiny granules. Target cells respond to these granules by surrounding and ingesting them, allowing the granules to release the DNA and deliver it to the host nuclei and chromosomes. Remember that old game, Pac-Man? It’s kind of like that.

The prepared target cells are immersed in a special solution with the selected DNA. A short but intense electric shock is then passed through the solution, resulting in small tears in the cell walls, which allow the new genetic material to enter the nuclei. Then, the cells are placed into another solution where they repair their torn walls, locking the donor DNA inside the cell and incorporating the new DNA into the host chromosomes. And, just like that, tadaa! -  a new gene.

Gene silencing
One method of “silencing” a gene responsible for an organism’s undesirable trait is to attach a second copy of the gene the wrong way around. This technique is used to prevent plants like peanuts and wheat from producing the proteins commonly responsible for human allergies. Another approach is to insert foreign DNA within a gene so as to “inactivate” it. This is the genetic equivalent of “What happens in Vegas, stays in Vegas.”

Gene splicing
Bacteria contain special enzymes that protect them against invasion by other organisms. These enzymes attack the foreign DNA by cutting it into precise sections and preventing it from being inserted into the bacterium’s chromosome.  Different bacteria produce different enzymes that cut DNA at different places. These cut DNA sometimes become “sticky”. Scientists make use of this neat trick by taking the sticky DNA and “pasting” it directly onto the target organism’s prepared DNA, which can then be inserted into cells to modify gene traits. Then a different enzyme is used to fuse the new gene sequences into the chromosome. Imagine making a collage of pictures from your trip to Europe and then putting the whole thing in a frame, behind glass. This is kind of like that.

The selected DNA is injected into a fertilized female egg cell through a very narrow glass capillary tube. The genetically modified egg is then transplanted into the prepared uterus of a female and allowed to grow to term. This is how transgenic animals are made. One word: Frankenstein.

Viral carriers
The selected DNA is added to a virus that will invade the target cells, but not cause cell damage or death. The virus is then allowed to infect the target. As the virus invades cells and replicates, the selected DNA is added to the target cells. Right. Because what we want more of is viruses thriving in our food supply.

Coming soon, Part 2 of G-M-Oh-Oh, where we take a field trip to our friendly neighborhood food store.