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tanarillTime for some Science!
Today I will explain about promoters. I am sure you know that the gene is transcribed by RNA polymerase to make mRNAs. But how does the RNA polymerase know where the gene starts? After all, if it started in the middle of the gene, you'd make only half a protein. And it is very expensive, energy-wise, for a poymerase to sit on the DNA and ride along like a cart on rails looking for a gene. So there must be another method.
This method is called the promoter. It is a short DNA sequence beginning about 40 base pairs from the actual transcription start, and it is like a little helipad for RNA polymerase to land on. Once there, RNA polymerase starts an mRNA. The promoter itself is not transcribed; it is another kind of important noncoding DNA, since without it you could never make any proteins. For this reason, a gene is considered to start at the promoter region.
One use for promoters is in genetically modified crops. When you put the insect-toxin gene into the corn, for example, you also need to add a promoter in so that it will be produced. The promoter used in almost every genetic modification made to plants comes originally from broccoli, and is very distinct. Checking for that sequence is how we test for genetic modifications, since the encoded protein might be very different, but the promoter is always the same.
As an undergrad, my class actually did the experiment with various corn-things, like Fritos and corn tortillas and, well, corn. Absolutely every product tested, excepting for the guaranteed non-genetically modified negative control, had the broccoli promoter.
And now you know!
Today I will explain about promoters. I am sure you know that the gene is transcribed by RNA polymerase to make mRNAs. But how does the RNA polymerase know where the gene starts? After all, if it started in the middle of the gene, you'd make only half a protein. And it is very expensive, energy-wise, for a poymerase to sit on the DNA and ride along like a cart on rails looking for a gene. So there must be another method.
This method is called the promoter. It is a short DNA sequence beginning about 40 base pairs from the actual transcription start, and it is like a little helipad for RNA polymerase to land on. Once there, RNA polymerase starts an mRNA. The promoter itself is not transcribed; it is another kind of important noncoding DNA, since without it you could never make any proteins. For this reason, a gene is considered to start at the promoter region.
One use for promoters is in genetically modified crops. When you put the insect-toxin gene into the corn, for example, you also need to add a promoter in so that it will be produced. The promoter used in almost every genetic modification made to plants comes originally from broccoli, and is very distinct. Checking for that sequence is how we test for genetic modifications, since the encoded protein might be very different, but the promoter is always the same.
As an undergrad, my class actually did the experiment with various corn-things, like Fritos and corn tortillas and, well, corn. Absolutely every product tested, excepting for the guaranteed non-genetically modified negative control, had the broccoli promoter.
And now you know!
no subject
Date: 2012-02-07 09:33 am (UTC)Mostly I don't care about GMO's except for the fact that more genetic variation = better survival rate, but, eugh, that gives me goose bumps.
no subject
Date: 2012-02-08 02:54 am (UTC)See, the single most common GM is to insert a protein which is toxic to the larva of the corn borer. These larva burrow into the stalks of the corn, which causes the corn to fall over and kills the plant. In order to kill them previous to this, much more toxic chemical had to be sprayed on the plants, since they'd only eat it when just beginning to bore into the plants. The pesticide would wash off the corn in rain and get into the ecosystem and poison all the things. But now, the corn produces toxin all the way through; and since it is a protein instead of an artificial chemical, rather than sticking around, the corn cells themselves digest it after a certain amount of time as part of natural protein turnover.
One of the professors here at my school is working on a different kind of useful GM. See, plants need nitrogen to grow, but not any nitrogen. Gaseous nitrogen, the stuff in the air, is very tightly bound up and unusable. A few billion years ago, a few bacteria figured out how to turn it usable, and every living thing owes them for this. Somewhat more recently, a few kinds of plants figured out a way to grow these bacteria symbiotically in their root systems; the bacteria get a safe home, and the plants get a neverending nitrogen supply. Not all plants can do this, and no staple crops (wheat, rice, etc.) can. This professor is trying to make GM wheat that can. This will remove nitrogen availability from the list of limiting factors, rendering huge portions of otherwise nutrient-poor soil (like the shrubland that the slash-and-burn farmers made of the Amazon) arable, and hopefully feeding millions.
Is this creepy? I think it is a good thing.
no subject
Date: 2012-02-08 04:04 pm (UTC)I'm just grumpy at agribusiness for manipulating genes for everything except taste. :|