Overview of Transcription

Hi in this video we're gonna be doing an overview of transcription. So transcription is the process of using D. N. A. As a template and that template D. N. A. Is used to synthesize RNA. So D. N. A. Is the template RNA as well as created. Now RNA Plymouth race is the enzyme that is responsible for transcribing the D. N. A. And turning it into RNA. And RNA copy. And there are many different types of RNA polymerase is and we'll talk about those in a different video but each RNA polymerase makes a different type of RNA. So those ribosomes RNA transfer RNA messenger RNA, non coding RNA is and there's different RNA polymerase is for each one of those are in a now it's always important in biology to understand the direction that things are happening in. So RNA transcripts are synthesized in the five prime to three prime direction. So this means that the new strand is produced five prime 23 prime. And how this happens is new R. N. T. P. So new RNA or nucleotides are added onto the three prime end. There's a hydroxyl group there and that hydroxyl hydroxyl group is what is important for adding new nucleotides in and that hydroxyl group is on the three prime end. So synthesize five private three prime now um D. N. A. Is double stranded. And that means that the information for the genes is actually found on both strands right there complimentary. But all that information is the same. But each gene is actually only you only transcribed using one strand. So even though it's a double helix, even though there's two strands, only one of those strands correctly transcribes or is used to transcribe the RNA. That will go on to create that protein. So this is important. Now. Oftentimes when we're talking about transcription we use two terms upstream and downstream. So what are those mean upstream means that it starts before the gene start site. So it's a sequence of DNA. That's before where the gene starts and downstream means there's an area of D. N. A. That is after the gene start site. So upstream comes before the gene starts and downstream comes after the gene starts. And just because this is an overview transcription occurs in three stages initiation elongation and termination. And these stages are slightly different between pro carry oats and eukaryotes. And we'll talk about those differences in other videos. But here we have an example. So here's the RNA polymerase RNA. P. That's what that stands for. And you see there's two strands of D. N. A. Um going five prime to three prime and three prime to five prime. Now the template strand. So this is the strand that's being used by the replay marais. See it's attached onto the template strand. Is that the RNA polymerase is using that strand to make RNA. And it synthesizes that five prime 23 prime. So you can see that the blue strand here is five prime. And the black strand which is the template strand is three prime here to five prime here? So, understanding this orientation is important and that means the template strand is what's used to create and this is going to be complementary. Right? These these are these are pairing here. So the template strand will be complementary and the coding strand will be the exact copy. So what I mean is that if you start out with D. N. A. And you have bases on each side, right? These are complementary, meaning that if you have a here, you're gonna have tea here and if you have C. Here, you're gonna have G. Here. Now when the RNA polymerase comes in it comes in here and it binds here, say R. N. A. P. That means that when it's synthesizing RNA and I'll use a different color, what it's doing is it's putting you here G. Here. And so this sequence isn't the exact same as the template strand but it is the exact same as the coding strand with the exception of RNA has uracil instead of time. Me. So if I were to let me scroll down and let's say I were to give a sequence. And I would say here's the template strand and here's the coding strand. And I were to ask what is the RNA sequence. So if the template strand is a T C G A T C. G. That would mean the coding strand is U A G C U A G C. Yeah. See so what is the RNA sequence? Can you if you had to guess what would it be? Is it is it the coding strand or the template strand? So if the coding strand is used right it would be. So the template strand is used because RNA polymerase binds to the template strand. Which means that the RNA that's red. Is you A G C U. A. G C G C. I don't know why I keep writing that is G. There we go. And so this is technically D. N. A. So I wrote you here but remember this is T. U. Is used for RNA. So notice here that the template strand and the R. N. A. Are complementary but the coding strand and the RNA are the same sequence with the exception of your sl and timing. So oftentimes you'll be given a question that says, you know, here is the coding strand. What is the sequence of the RNA? Well if you're given the coding strand, know that it's the exact same sequence except for your sale is exchanged for that I mean but if you're given the template strand that's the complementary and that's the difference between the two. So often times people see questions like this, so that's the overview transcription. So with that let's move on

Transcription is the process of which of the following?

• A. DNA → Protein
• B. DNA → RNA
• C. DNA → DNA
• D. RNA → DNA

Only one strand of DNA is used during transcription of a gene.

• A. True
• B. False

If a DNA sequence is upstream of where the gene is, where is these sequence?

• A. Before the gene
• B. After the gene
• C. In the middle of an intron
• D. At the start of the first exon