 Get ready for some fun. We're going to look at how transcription takes place. Are you ready? First of all, who did I say is the star of the show? That would be my friend. RNA polymerase. DNA polymerase was the star of the replication show. RNA polymerase is the star of the transcription show. RNA polymerase is going to take the information in DNA and use that information to build a messenger RNA molecule. Again, I want to remind you that the RNA polymerase, it's an enzyme and it's made out of proteins. And you can see that this is what it actually looks like. True story. How do they figure this stuff out? Isn't that fantastic? All right. So, ha! Does it look familiar? It's a different color, just in case you were worried. RNA polymerase, this time, we're not completely splitting the DNA. This time, we're going to open the DNA up in a certain place and we're going to transcribe just one piece of it. There are molecular markers that RNA polymerase can identify or respond to to know where do I start? Where is the beginning of a gene that needs to be translated into a protein? And in order to do that, there are some helpers. RNA polymerase makes use of transcription factors to go in and separate, the transcription factors actually separate out the DNA double strand. So, they create like a little opening. So, you could take a rope or a piece of yarn and you know how it twirls around itself, but you can actually separate the little twirly pieces and peek inside and that separation, that's what's happening during transcription. During replication, remember the whole thing splits and the two sides of the DNA molecule literally separate forever and they don't even come back ever. It's not the case with transcription. So, if I were to make this more perfect, on each end, you would have pieces that are still attached. So, it's like a little opening like this or a rope, however you want to think about it. Okay, transcription factors do a fantastic job of keeping the DNA molecule apart. Still, DNA polymerase needs to be working with, I mean, I knew that there was something, RNA polymerase, because that's who this is. RNA polymerase needs to be working with RNA nucleotides. Can you tell that I have RNA nucleotides here? Of course you can. First of all, what is this light pink color when we could have this dark pink deoxyribonucleic acid nucleotide and instead we have this light pink ribose ribonucleic acid nucleotide. All of these are RNA nucleotides that are being added on. However, they're being added on in the same pattern and with acceptable like, oh yeah, of course that's the pattern. Of course that's how we're going to do this all the way through. You could, I could give you a strand of DNA and you could be like, boom, I can tell you exactly the messenger RNA strand that's going to be transcribed from that. Once you get to the end, it's this simple. There's a little sequence that says, yo dude, you're done. And then RNA polymerase says, it's what I'm talking about, I'm done. And then the messenger RNA molecule falls off of the DNA and the DNA behind the messenger RNA is actually going to zip back up just like, like the transcription factors are going to fall off and we're going to zip back up. If the transcription factors weren't there this would not be possible because the DNA molecule wouldn't unzip or wouldn't stay unzipped. We might be able to try and make it unzip but it wouldn't stay that way. You might think, okay, done, that's the end of the story and that's not exactly the case. There are some things that we're going to have to do to the messenger RNA in order to get it ready. These things, these modifications are modifications that happen in eukaryotes. Prokaryotes don't do these modifications. So their messenger RNA molecules are not nearly as hip and cool as ours because they get a five prime cap. What? Look, it's a rainbow cap. That's because we're in Humboldt County. And not just a cap, I mean, when you go out I know you need a rainbow cap on your five prime end but you also get woo, woo, a poly A tail. Of course you get a poly A tail. The party isn't a party until you are wearing your five prime cap on your poly A tail. Now the messenger RNA is done. Now I say the messenger RNA is done. There are a couple of other things we're going to talk about in the next section that give us like crazy potential for ways of making different kinds of proteins from just a few genes. We'll talk about that in a second. Once we have our five prime cap and our poly A tail we can go head off where to the cytoplasm. We're going to go find ourselves a ribosome. And where are we right now in the nucleus? Let's see if this guy, oh, he doesn't head off. He doesn't zoom away. I'd like to see him go like that. You want me to do that again? That was a little bit higher pitch. I better stop right now. Let's talk about the post-transcriptional modifications that can take place. Seriously, I didn't push stop. I hate it when I do that.