[MUSIC] Hello and welcome back. It's been a little while. Today, we're going to discuss biotechnology. If we consider biotechnology at its most basic level, humans have been doing it for thousands of years. Farmers have picked the best seeds for selective breeding of farm crops based on factors such as the crops insect resistance. The ability of the crop to adapt to a climate, and of course taste. Consider a modern corn, it's ancestor, a plant called teosinte, barely resembles what you probably eat off the cob. Through artificial selection, farmers only planted seeds from corn that had the traits they were looking for. Big, sweet and yummy. Before these farmers had any idea what DNA was, farmers were selecting for specific genes through a selection of preferred phenotypes. Today we use DNA technology to produce medicines, improve food quality, diagnose and treat diseases and even help solve crimes. In the world of modern genetics scientists can create transgenic organisms. A transgenic organism is an organism that received one or more of its genes from another organism. One example of how we can use our ability to transfer genes from one organism to another is to synthesize or create therapeutic hormones. In 1982, Humulin came on the commercial market. Humulin is a human insulin produced by bacteria. Humulin became the first recombinant drug approved by the FDA. Before Humulin, insulin was very hard to come by because it had to be isolated from animals, which was incredibly expensive and time consuming. There were also ethical implications, since the hormone had to be isolated from the pancreas of cows and pigs. So how is bacteria that synthesizes human insulin created? First we have to consider where the genes come from to insert into these transgenic bacteria. So, the challenge is to locate the specific gene that encodes for the protein that you want the bacteria to synthesize or make for you. In the case of insulin we need to insert the human insulin gene into bacteria for it to be synthesized. But, bacteria aren't going to be able to modify the insulin protein like human cells do in our pancreas. So, we have to insert the insulin gene as two separate genes and then combine the two protein products to create a functional insulin hormone that resembles the human insulin protein. The insulin gene is inserted into a plasmid. That's a piece of bacterial DNA. Then, this plasmid is inserted into the bacteria. But, we have a problem. The issue is, the bacteria isn't just going to happily synthesize a bunch of protein, without some convincing. So, we have to do some co-manipulating to change the way that the bacteria responds to the plasmid. So we're going to insert a strong constitutive bacterial promoter, right before the insulin gene. And that's going to tell the bacteria to increase transcription of that insulin gene, and the fact that the promoter's constitutive means, it's always turned on. Bacteria like E coli replicate very quickly. E coli replicates every 20 minutes. What that means is that every 20 minutes, E coli creates a clone of itself. That means that the genes that you incorporate in the bacteria will be copied every 20 minutes. And, what's also nice is the bacteria are pretty low maitenance in a lab. So you can insert a wide variety of genes in a bacteria, and have them work as protein producing factories. But, not making just protein, they can also replicate the gene you inserted. And bacteria can produce a wide range of proteins that can treat a multitude of human diseases. One such example is hemophilia. Bacteria can produce a clotting factor called factor 8. People with hemophilia can be treated without needing a blood donor now. I want to now move on and discuss how we insert genes into the plasmid to create recombined DNA. Enzymes are used to cut and paste to create this recombinant DNA. What we use are a class of enzymes called restriction enzymes. These are enzymes that are used to cut the plasmid in specific regions. These restriction enzymes are isolated from bacteria. Bacteria synthesize restriction enzymes, because bacteria can be infected by viruses like humans can be infected by viruses. But bacteria don't have immune systems like we do. What bacteria have to protect, protect themselves from these viruses are restriction enzymes that'll cut up any foreign DNA at very specific sites. We can manipulate these restriction enzymes, and use them to cut a plasmid to allow us to insert our gene of choice. In the lab, we'll use that restriction enzyme to cut the plasmid, then we'll insert our genes, and now we have to paste our genes into the plasmid. And what we'll use is an enzyme called DNA ligase, and that pastes the DNA fragments together. So the enzyme DNA ligase is normally found in the cells of your DNA as it's undergoing DNA replication. In addition to creating transgenic bacteria, we can also create a wide range of transgenic plants. For this, we're going to use something called the TI plasmid. TI stands for tumor inducing. So we can create transgenic plants by transferring genes into plants using that Ti plasmid. That plasmid's found in nature in a bacteria called Agrobacterium. In nature, this bacterium infects plants and induces a tumor to form, allowing a bacteria to proliferate, since the tumor increases the number of plant cells for the Agrobacterium to infect. Bacteria does this by using the genes on the Ti plasmid in Agrobacterium to undergo a process Horizontal Gene Transfer. This is quite different from the process we discussed before where genes are passed from your mother and father to a child in a process called vertical gene transfer. In horizontal gene transfer, genes are transferred across different organisms. In the lab, we'll incorporate genes into the plant that can allow for insect resistance, resistance to drought, resistance to frost. We can even insert genes to improve flavor, fruit or vegetable size, nutritional value and shelf life, to just name a few. These genes we insert into the plants are really only limited by the imagination. One example of a gene that's been inserted into plants that Dr. Saint-Ledger will discuss is the BT toxin gene from Bacillus thuringiensis, a bacteria. When I say toxin, you may be concerned that this could harm you or other humans, but what's reassuring is that this toxin only affects insects. The issue with conventional chemical pesticides are the cost of purchasing the chemicals, the cost of applying and reapplying, and a lot of non-target beneficial insects could be killed, not to mention the environmental impacts of these pesticides. We can cut the Ti plasmid with restriction enzymes and with DNA ligase, paste in the BT toxin which is coded for by the cry gene. Cry stands for crystalline BT prot, BT protein toxin. If you spray corn with conventional pesticides, a common insect pest of corn, the European corn borer is protected from the insecticides, since it's hidden inside the husk of the corn. But with transgenic BT corn, expressing the cry gene, the corn borer will die soon after munching on the transgenic corn, since the sweet treat contains the BT toxin. Another benefit is that the BT toxin has no side effects on humans, which is not true on many chemical insecticides. And since insects trying to make a bite out of the corn will only be, will only be affected, this shouldn't harm other beneficial insects. So the Ti Plasmid can also be used to insert genes into a wider range of plants such as soybean and rice. Some planes are resistant to be infected by the TI plasmid and in that case a gene gun can be used to insert foreign DNA into these plants. The DNA you want inserted into the plant is placed in gold particles and literally blasted into the cells of these plants and some of these plants cells will take up the foreign DNA. So we talked about how to make transgenic bacteria and transgenic plants, and our next lecture we'll discuss how to create transgenic animals. [MUSIC]
