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Genetically Modified Organisms

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

Genetically Modified Organisms (GMO) are organisms with altered DNA. This is often done by adding a gene from one species to another and is extremely useful in labs for drug creation, agriculture and medical research. Scientists alter DNA by "cutting" the gene using a restriction enzyme, "gluing" it into vector DNA using the enzyme ligase, and inserting the vector DNA into the host cell.

Sometimes when you're reading in a textbook or listening to the news you may hear something being mentioned called a GMO what does that stand for? A GMO is short for Genetically Modified Organism, and these are organisms living creatures that had their DNA altered. Generally you create a GMO by adding a DNA gene from one species into another. Why would be anybody ever want to do this? Well a lot of times it's used for research if you're trying to figure out how Alzheimer's works ,one of the best way to do so is to take a gene that you believe occurs all time as in humans and put it into some laboratory animal that you can do experiments on that you couldn't possibly do on a human.

You can do this to create new products for example one of the first most successful examples of creating a GMO was the creation of a bacteria that produced human insulin and that's something that's monumental and it led to the development of ways to treat diseases that never existed before for example diabetics are able to get insulin that's human insulin but its being made by a bacteria. There's many other examples of these kinds of GMO's in agriculture there's a lot of different versions of soybeans and corn that have been genetically modified. One of the more common ones is a modification that allows that corn to make its own pesticide not a pesticide that affects humans but one that targets the insects that eat the corn what this means is that farmers don't have to spray pesticides all over their fields instead if the insect starts to munch on the corn they die and so they leave the corn alone and the producers of this will say "this is awesome for the environment this is great because it means we don't have to spray nearly as much pesticides and its wonderful in that way." People who are against it will say "well what happens when this gene gets from the corn which we don't want pests insects to eat into wild plants that we do want those insects to eat? What if it starts killing off creatures that we consider are important to the Ecology?" And that's a question that is still being debated.

There is some people who have started using the this idea to investigate ways to create vaccines in potatoes and that's incredible because if you think about it vaccines are great way to stop diseases like small pox or whatever but they require large investments in manufacturing plants in chemical industries that a lot of developing countries can't afford. They also require refrigeration and trained health people to do the injections well what if you can put the vaccine into a potato then you hand the potato to somebody in a developing country and they know how to make potatoes you put them on the ground they grow then you take potato you cut the potato you eat the potato you're vaccinated, no refrigeration no training there it's a great concept whether or not it becomes a reality that's another question so how is this amazing ability to modify the genes of living organisms done?

One of the basic process is fairly simple to describe. First you cut and isolate the DNA that you want. You separate it out from the rest of the DNA from your donor organism then you glue or ligate that into a special kind of DNA called a vector DNA that can get the desired DNA into our new host cell. You then insert it into the host cell those are a variety of ways that can happen then you grow your host cell that hopefully has your new DNA into it in and then finally you check to see whether or not it's showing the new trait it's expressing it so let's take a closer look at that.

Now here we see a couple of different sources of DNA in blue we have our vector DNA it's a small circular DNA called a plasmid that's commonly used to do genetic modifications of bacteria. Over on the right hand side you can see DNA in green that's our donor DNA. Now the gene that we're actu- actually interested in is the one in the darkest green way over to the right and we can see that we've cut the DNA and it's falling into several pieces we cut our plasmid or vector with the exact same restriction enzymes that create this little staggered ends and then by mixing it together in the same test tube with ligase enzyme which joins or ligates DNA fragments together we have now created new combination of vector DNA in blue and our donor DNA in green. This recombinant DNA we can then insert into a bacteria and you could do that in a lot of different ways. Plasmids you can get into a bacteria through a process called heat shock which is a form of causing transformation which essentially your using heat to shock the bacteria into taking in the plasmid.

There's many other methods one involves using viruses where you put the desired DNA into a virus and then you just let that virus infect the host cell, so now we have a bacteria that's got a recombinant DNA and we just feed it and you can see here it's got it's own in red chromosome well it falls in the orders of those genes in the red chromosome and it copies itself and it winds-up also copying the plasmid and so that when it does cell division you windup with two cells identical to the original one, both of them have been genetically modified and this allows us to create large numbers of our genetically modified organism. Finally we check for expression which with bacteria it's pretty simple you squirt them out into a Petri dish and you look to see, are they showing the new trait that we desired? For example if our gene was instructions on how to build a red protein, we can see that four of our little blobs of bacteria are showing the effects of this red protein. Now it's a little bit more complicated in reality and when you're working with eukaryotic cells like ours, it becomes a lot more complicated but the same the basic process is still the same where you cut DNA, join it together with the vector, get it into the target organism and then allow it to grow and check to see if you're successful.