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Time 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!
