Steps of Transcription

in this video, we're going to begin our lesson on the steps of transcription. And so the process of transcription actually consists of three steps. The very first step is going to be initiation of transcription. The second step is going to be elongation of transcription, and the third and final step is going to be the termination of transcription. And so moving forward, we're going to talk about each of these three steps of transcription in their own separate video, starting with initiation. And so the initiation of transcription initiation is referring to the beginning of transcription. And this involves the RNA prelim Aries, binding to the promoter region on the DNA and separating the two strands of DNA. And so when those two strands of DNA are separated, that is going to allow the second step of transcription to begin. Now it turns out that transcription in eukaryotes and prokaryotes is a little bit different. And in pro Kerasiotes, the RNA preliminaries, which is the main enzyme involved in transcription, is going to bind to the promoter region on its own. However, in eukaryotes transcription factor, proteins are required for the RNA polymerase to bind to the promoter and we'll be able to see that down below in our image. Now again, the unwinding of the DNA by the RNA polymerase is going to expose the DNA template strand, which the RNA polymerase can use the DNA template strand as a guide toe build the Arna. And so if we take a look at our image, which you'll notice is on the left hand side, we're showing you initiation of transcription and pro Kerasiotes. And on the right hand side, we're showing you initiation of transcription and eukaryotes. And so, in the initiation, we know that the DNA polymerase is going to bind to the promoter and separate the two strands of DNA. And so here, in our image, the Pink Circle is representing the Arna prelim Aries, and the RNA polymerase is going to bind specifically to the promoter region on the DNA. And so that's what you can see here. The are Nepal. Emery's is binding specifically to this promoter region on the gene, and so it will then unwind the DNA separating the two strands, exposing the template strand of the DNA you can also see downstream. Over here you can see the Terminator, which is going to be involved in the final process of transcription. Now, over here on the right hand side, you'll see the same process, initiation of transcription, but in eukaryotes. And really, the main difference that we're focusing on here is that in order for the RNA polymerase to bind to the promoter region and eukaryotes these other proteins that air we're representing as these yellow shapes here, uh, are required and those are the transcription factor proteins, and so in eukaryotes are in April. Emery's requires transcription factor proteins, uh, toe bind to the promoter, and, uh, that will allow for the RNA polymerase to bind. And so in, uh, the eukaryotes here in the background, you can see that the transcription factors are bound and that helps recruit the are Nepal emery so that the Arna polymers can also bind to the promoter. And then again, uh, transcription initiation is going to allow for the second step of transcription to begin, which is elongation. And so we'll talk more about elongation the second step of transcription in our next video. So I'll see you all there

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

in this video, we're going to talk about the third and final step of transcription, which is the termination of transcription. And so termination is just a word that's referring to putting something to unending. And so the termination of transcription is the process that results and the end of transcription to produce an RNA molecule. Now it turns out that pro Kerasiotes and eukaryotes they actually differ in the way that they terminate transcription and eukaryotes. Specifically, eukaryotic termination forms a pre mature our DNA molecule and this premature. Our DNA molecule is not the final molecule and eukaryotic organisms. The premature Our DNA molecule and eukaryotic organisms requires further modification through Arna processing, which we'll get to talk more about as we move forward in our course. However, in pro Kerasiotes, the RNA molecule that's formed is not a premature Arna, and it does not require Arna processing. Uh, the premature Arna is on Lee going to be found in Eukaryotic organisms. And so if we take a look at our image down below at the termination of transcription, which you'll notice is that the are Nepal, Emery's is reaching this Terminator sequence here and the Terminator sequence on the DNA is going to initiate the process of termination and ultimately termination results in the RNA preliminaries being released on the RNA molecule being released now again in pro carry attic organisms, the RNA molecule is ready for translation immediately. However, in Eukaryotic organisms, the RNA is a premature Arna, a pre m Arna, and this is not going to be the final version of the RNA in eukaryotic organisms. This Rene would have to undergo Arna processing in Eukaryotic organisms before translation can take place. And so again, this is on Lee going to be applicable for eukaryotes, not for pro Kerasiotes. And so this here concludes our breathe introduction to determination of transcription. And we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.