1) Elongation of Transcription

by Jason Amores Sumpter
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in this video, we're going to talk about the second step of transcription, which is the elongation of transcription. And so elongation is really just a word that means to elongate or make something longer. And the something that's being made longer is the RNA itself. And so elongation is the process where the RNA polymerase enzyme is building or synthesizing or elongating an RNA molecule. And so it does this by base pairing free RNA nucleotides, that air floating around in the cell with the DNA template. And so, by the end of the process, the RNA molecule that's being built is going to be carrying the message that's encoded by the DNA. Now. The RNA polymerase enzyme, which is again the primary enzyme involved in transcription, is going to continue to move across the gene, unwinding the DNA as it moves and building the RNA as it moves in the five prime to three prime direction of the RNA. And so if we take a look at our image down below at the elongation of transcription, you can see that the DNA polymerase enzyme, this big pink circle, is now bound to the promoter region on the DNA and, uh, the RNA polymerase has unwound the DNA, so you can see that the DNA on the inside is unwound and it's beginning to elongate or build that are in a molecule by pairing free RNA nucleotides. These little guys here that air floating in the cell. Each of these little squares represents free RNA nucleotides, and the RNA polymerase incorporates them into this growing RNA strand by pairing these RNA nucleotides with the DNA template strand. And so this are in a polyamorous is transcribing in this direction towards the right, so it will continue to transcribe the coding sequence. And so this is representing the process of elongation. And, of course, during elongation, the Marna the molecule are in a molecule is growing, it is elongating, and it's elongating from its five prime in to its own three. Prime it and the RNA polymerase will continue to elongate in this direction. Continue to transcribe the gene until it reaches this terminator sequence that you see on the end here, and we'll talk Maura about this termination process and our next video. Now, one thing that's important to note here is that in eukaryotic organisms, the RNA that is first transcribed, is not the final Arna. Instead, it's a premature Arna or just a pre m Arna, and so we'll get to talk Maura about the pre m r n a. Later in our course now, it's also interesting to note that a single gene can actually be transcribed simultaneously by several RNA. Polymerase is to make more Arna if it's needed. And so while this Marna here is being built by this Arna preliminaries, it is possible for a second RNA polymerase to come and bind to the promoter and to transcribe this gene simultaneously, where there's multiple RNA molecules being built simultaneously from the same gene. And so that is just something to keep in mind. And so this year concludes our brief introduction to the elongation of transcription. And so in our next video, we'll get to talk about the third and final step of transcription, which is the termination of transcription. So I'll see you all there