in this video, we're going to begin our lesson on eukaryotic RNA processing and splicing, and so recall that we mentioned in some of our previous lesson videos that, unlike pro carry attic Marna, it turns out that you carry ah, tick Marina is going to require further modification upon transcription termination. And that's because eukaryotic organisms upon transcription termination. The Mara is not fully mature. It's a premature Marna, otherwise termed a pre m Arna. And so this pre mRNA that's originally formed in Eukaryotic Organisms is the Eukaryotic Marna, before modification via our DNA processing and splicing. And so are in a processing and splicing are just these eukaryotic processes that convert this premature Marna or pre mRNA into a fully mature Marna that's actually ready for translation. And again, this is on Lee, a process that applies to eukaryotic organisms not too pro carry attic organisms. And so if we take a look at our image down below notice over here on the left hand side, this is representing the premature Mara or the pre M R N A that's originally formed during Eukaryotic transcription. But this pre M R A is premature. It's not ready for translation. In order to prepare this pre mRNA for translation, it has to undergo Arna processing and splicing, and so are in a processing and splicing are going to be these eukaryotic processes that help convert the pre M Arna into a modified version of the M R N A. That is ready and fully mature and ready for translation. And so, as we move forward in our course, we're going to talk about exactly what's entailed in our DNA processing and an RNA splicing toe. Help convert the pre Amarna to this modified Mara over here, and so we'll get to talk more about that as we move forward, so I'll see you all in our next video.
1) RNA Processing
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in this video, we're going to talk about RNA processing. And so Arna processing Onley occurs in Eukaryotic organisms, not in pro carry attic organisms. And so eukaryotic RNA processing involves to events that are gonna alter both ends of the premature Mara or the pre M Arna. And so the first event is going to be the addition of a five prime cap, which is really just a modified guanine nucleotide that's going to be added specifically to the five prime end of the pre mRNA. And then the second event that's going toe alter. The end of the pre Amarna is the addition of a poly a tail, and the poly A tail is really just a sequence of a bunch of adding nucleotides that are gonna be added specifically to the three prime end of the pre m r N A. And so both of these alterations are going to modify the ends of the pre Amarna. And so if we take a look at our image down below, which you'll notice is over here on the left hand side. What we've got is our premature Mara, our pre m Arna immediately after transcription and so this pre m r N A. We know that in eukaryotic cells is going to go undergo Arna processing, which involves modifying the end of the pre Amarna so you can see the ends are being modified. The first modification involves the addition of a five prime cap, which is added to the five prime end of the RNA molecule. And again, the five prime cap is really just a modified guanine nucleotide. Now on the three prime end of the Arna molecule, it is also going to be modified. But with a poly, a tail and the poly, a tail is just a stretch of a bunch of adding nucleotides. That air added to the three prime end of yarn a molecule. Now you might be wondering. Why is it that the five prime cap and the poly a tail need to be added to the RNA? And so it turns out that the five prime cap and the poly a tail actually share several important functions, including the following functions that were listing down below. The five prime cap and poly a tail are both important for facilitating exports of the Marna from the nucleus where its first transcribed in eukaryotic organisms to the cytoplasm where the RNA molecule needs to be in order for translation to take place, which again we'll talk more about translation later in our course. But the pop five Prime Captain Poly a tail are really important toe export the Marna, from the nucleus to the cytoplasm. Now the five prime cap in poly a tail are also really important to protect the Marna from degradation by enzymes. And so the addition of the five prime cap and the poly a tail helps to again protect the Marna from degradation by enzymes that might otherwise degrade the RNA. Now, lastly, the five prime cap and poly a tail are both important for helping ribosomes attach to the Amarna for translation to take place. And so we'll be able to talk again, Maura, about translation later in our course. But these ribosomes are cellular structures that are important for translation. And so these ribs owns need to be able to attach to the marina and the five prime Captain Poly a tail play a role in that attachment. And so, uh, this here is going to conclude our brief introduction to Arna processing and so in our next video will be able to talk about RNA splicing, so I'll see you all in that video.
Which of the following processes occurs in eukaryotic gene expression?
mRNA, tRNA, and rRNA are translated.
A cap is added to the 5′ end of the mRNA.
Adenine nucleotides are added to the 5’ end of the mRNA.
RNA polymerase requires tRNA to elongate the molecule.
A mRNA poly-A tail:
Marks the RNA for degradation.
Protects the mRNA from degradation.
2) RNA Splicing Creates Mature mRNA
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in this video, we're going to talk about RNA splicing and how RNA splicing helps to create mature mRNA molecules. Now recall that RNA splicing is a eukaryotic process that Onley occurs in eukaryotes but does not occur in pro Kerasiotes. And so it's important to note that even within Eukaryotic genes within the DNA of eukaryotes, there are regions that air called entrance, and Exxon's now will introduce what the's entrance and Exxon's are very shortly here. But it's important to note again that these eukaryotic genes have entrance and Exxon's. And so when eukaryotic genes are transcribed, they're going to be transcribed into the premature Mara. And so the premature or the pre Marna is going to contain entrance, and Exxon's Now RNA splicing is going to be the eukaryotic process that is important for removing some of the regions of the pre Amarna. Specifically, the entrants are going to get removed, and RNA splicing involves the reconnecting of the remaining regions of the pre Amarna, which are going to be the Exxon's and so notice that down below. We're saying that entrance, which starts with I n are going to be non coding regions of DNA and RNA, meaning that they do not actually code for amino acids or proteins. And these non coding regions of DNA Arne are going to intervene or interrupt the coding regions of the DNA and Arnie. And so these entrance do not get translated. They do not get turned into protein. Now. The entrance, because it starts with I n the I n and Entrance, can hopefully help remind you that they are intervening and interrupting, which also start with I n. Now the Exxon's. On the other hand, starts with E X and Exxon's are coding regions of the DNA and RNA that ultimately do get expressed. And so that means that they do actually get translated into protein. And so we'll get to talk Maura about translation later in our course. But ultimately what we're seeing here is that within the DNA and RNA, originally, there will be entrance and there will be Exxon regions, the entrance need to get removed, and the Exxon's need to be reconnected and get expressed. Now, the splices, um, is the large cellular complex of RNA and protein that's gonna be responsible for removing the entrance and splicing together or reconnecting the Exxon's And so if we take a look at our image down below, we could get a better understanding of these entrance and Exxon's and RNA splicing. And so it says here that the spices, um, is going to remove entrance from the prima RNA transcript after transcription. And so, if you take a look at the top here, what this is representing is the DNA. The Eukaryotic DNA, which we know eukaryotic DNA has a promoter region, which is going to initiate transcription. And it has a Terminator region at the end, which is going to terminate or end transcription. And in between what we have is the coding region. But in this coding region, there are some regions that are going to be Exxon's and other regions of the DNA that are going to be in trans. And so the Exxon's in this image are represented by these reddish regions, and the entrance are, of course, represented by the bluish regions. And so the Exxon's and entrance are found in the d N A. And so when the DNA gets transcribed when it undergoes transcription, the premature Mara is going to be built with premature Marna transcript or molecule will be built. And so which you'll notice is that the premature Marna contains both Exxon's and entr ons. And again, the entrance are kind of intervening or interrupting the coding regions so you'll see the entrance are kind of in between and interrupting the Exxon's, which ultimately get expressed. And so if you zoom in over here, what we're showing you is the splices own formation, which recall that the splices home is is really large, complex off RNA and protein, responsible for removing entrance and splicing together or reconnecting the Exxon. And so the spices home here is forming. And which will notice is that the blue region, the Exxon's are getting pinched off and they're ultimately going to get removed. And the Exxon's these red regions here are going to get reconnected. And so this is here representing RNA splicing. And so our RNA splicing ultimately is going to lead to a mature M r n a transcript. And so when you take a look at these mature M r n A transcript, you'll see that they've been processed, are in a processing has occurred because it's got the five prime cap over here. Guanine cap and It's got the poly a tail and noticed that all of the entrants have been removed. All of these blue regions have been removed through RNA splicing, and the Exxon's have been reconnected and the Exxon's ultimately get expressed, which means that they will be translated into a amino acid sequence. Toe ultimately helped form a protein, which is down below now. It turns out that there is alternative our DNA splicing there are There's something known as alternative RNA splicing, which means that single genes can actually be spliced in different ways in order to give multiple products. And so that's what we're showing you up above. How this premature Marna transcript can actually be spliced in multiple ways where, UM, which will notice, is over here. Exxon's 123 and four are all being expressed. But over here on the right hand side, Onley Exxon's 12 and four are being expressed. An Exxon three is not being expressed because, with alternative splicing, Exxon three actually acts as an in Tron with this alternative splicing. So Exxon three was removed, and so what we can see here is that in on some scenarios, Exxon's may actually act as Exxon's. But another scenarios. Some Exxon's will act as entrance and get removed. And so we have a shorter, uh mature Marna transcript or M R and a molecule here because it's missing Exxon. Three. Notice there's no Exxon three, and so that's going to lead to a shorter amino acid sequence upon translation, and that will ultimately lead to a different protein with a different shape. And so this protein and this protein are different proteins with different structures, different shapes and ultimately different functions. And so what you can see is that you can have a single gene, a single segment of DNA that can lead to multiple protein products, depending on how the RNA spliced through alternative RNA splicing. And so this here concludes our brief introduction to RNA splicing and how it helps to create a mature Marna that's ready for translation. And again, this Onley occurs and eukaryotic organisms. And so 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
The regions in DNA & RNA that encode actual gene products are known as:
Additional resources for Eukaryotic RNA Processing and Splicing