1) Initiation of Transcription

by Jason Amores Sumpter
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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