in this video, we're going to begin our lesson on eukaryotic post transcription ALS regulation. And so you carry outs. Regulate gene expression at the post transcription all level in three different ways that you can see number down below 12 and three. And so the first way that they regulate their gene expression at the post transcription a level after transcription is complete is through alternative RNA splicing. An alternative RNA splicing is going to result in different protein products coming from the same M RNA transcript or the same gene. And we'll talk more about alternative RNA splicing as we move forward. Now the second level of post transcription ALS regulation and eukaryotes is RNA processing by adding a five prime cap and a poly a tail to the M R N A in order to protect the RNA from degrading enzymes. And again, this is an idea that we'll talk more about moving forward as well. And then the third level of post transcription regulation and you carry outs is that the M R N A can actually be tagged for degradation or transcription can be blocked, uh, from the m r n. A transcription of the M RNA can be blocked by small, non coding RNA molecules, and we'll talk more about these small, non coding RNA molecules as we move forward as well. And so this year concludes our brief introduction to Eukaryotic post transcription all regulation, and we'll be able to talk about all three of these different levels as we move forward, so I'll see you all in our next video.

in this video, we're going to talk about the first level of post transcription all regulation in you curios, and that is alternative RNA splicing. And so recall that way. Back in our previous lesson videos. We already covered alternative RNA splicing. And so, if you don't remember anything about alternative RNA splicing, then make sure to go back and watch those older videos before you continue here. And so recall that eukaryotes require post transcription allow modifications like RNA splicing, which can alter gene expression. And so alternative splicing is really when different M RNA molecules are produced from the same premature RNA, a molecule or the same pre m R n A. And so another way to be able to phrase alternative splicing is because there are different M RNA molecules produced that's going to lead to different proteins being made from the same gene and so different M RNA molecules will lead to different proteins being made, and these different M RNA molecules are made from the same premature M r n a or the same gene. If you will now recall that the splices home is the complex RNA protein complex that is going to remove entrance from the pre m r N a, uh, and spliced together the Exxons. And so if we take a look at our image down below, over here again, we have our miniature map and you can see that we're focusing on RNA processing, and this is going to be a form of post transcription, all modifications and regulation. And so RNA processing here is also going to include the splicing here that we're referring to and so up at the top here. What we have is the D. N a. The specific gene of interest, and within the gene, the red regions here represent Exxon's that are going to be sliced together, and the blue regions represent entrance that are going to be removed. And so I noticed that when the gene is first transcribed through transcription, it's a pre M RNA molecule or pre M RNA transcript that is formed and the pre M RNA molecule is, uh, not going to be, uh, fully mature. M r N A. It must undergo splicing. And so over here, what we are resuming into is the splices own formation, which is going to be an assembly of, uh, complex of RNA and protein that will come together to remove the entrance, remove the blue regions and spliced together the red regions, the Exxon's. And so that's what we're referring to. Here is RNA splicing and alternative RNA. Splicing is when RNA splicing can occur in multiple different ways. There are alternative pathways for RNA splicing to occur, and so here in this image we're focusing on just two different alternative pathways for RNA splicing to occur. The first RNA pathway RNA splicing pathway is over here on the left hand side, which is showing you Exxon's 123 and four all being expressed, uh, and this is going to be the fully mature. This is the mature mRNA that's ready for translation. And so this is one possibility for the RNA to get spliced, and that would create this particular circular protein product upon translation. But the alternate RNA splicing pathway over here notice has a different, mature mRNA transcript where Exxon three notice is not available. Over here, it's not present. And so Exxon three acted as an in Tron, uh, in this alternative RNA splicing pathway, and so Exxon three was removed as an entrance, and so only Exxon's 12 and four are available over here. And that creates a shorter Polly Peptide chain, and that ultimately leads to a different protein. And so, by filtering and controlling alternative RNA splicing, a specific gene product can be redirected to create a new gene product. And so this is a way of regulating gene, uh, expression. And so this is a post transcription all, uh, method because the alternative RNA splicing is occurring after transcription has occurred. And so this here concludes our brief review and introduction here of alternative RNA splicing, and we'll be able to get some practice applying this as we move forward and talk about the other forms of post transcription all regulations, so I'll see you all in our next video.

in this video, we're going to talk about the second level of post transcription regulation, which is mRNA protection in the cytoplasm. And so mRNA transcripts must be transported to the cytoplasm of the cell in order for the mRNA transcript to be translated by ribosomes and create a protein product. But the problem is, is that the cytoplasm actually has many RNA degrading enzymes. And so the M RNA transcripts. When they go out to the cytoplasm, they are at risk of being degraded by these RNA degrading enzymes. Now these are in a degrading enzymes are there to help destroy foreign viral RNA molecules so they are going to act as a defense mechanism against viral RNA molecules. Now, in order for the mRNA transcripts to be protected, the M RNA needs to be processed so that it has a five prime cap added as well as a poly a tail added as well. And so the five prime cap and the poly a tail, which is added to the three prime end of the molecule. Um, that is going to protect the M RNA from degradation by enzymes. And so this degradation feature and, uh, non and protection feature degradation and protection is a way of regulating gene expression. And so let's take a look at our image down below to get a better understanding of this. And so notice the example here says that M. R N A. Is protected from degradation by cytoplasm enzymes with a five prime cap and a poly a tail. And so RNA processing, which is the addition of the five prime Captain Poly. A tail occurs within the nucleus, but of course the RNA needs to be transported to the outside into the cytoplasm of the cell. And so it needs to be transported outside the nucleus into the cytoplasm of the cell. And so that's what you see here. Here we have the nucleus. This entire box here is representing a cell, and within the cell we have the nucleus of the cells right here and within the nucleus. You can see we have our mature M RNA here, and it must be transported out of the nucleus. Now if the mRNA is not protected, if it does not have a five prime cap in a poly a tail, then it's going to be an unprotected mRNA. And that's going to lead to degradation. So the unprotected M R N A. Is degraded over here and notice that it's being chopped up into a bunch of tiny little pieces. And then, in that case, the final gene product, the protein is not going to be created. And so this is a way of turning off. The gene is through, uh, making sure that the RNA is unprotected. That will turn off the gene. Now, of course, if the R N A is properly protected with the five prime cap and the poly a tail, then we have a protected M RNA that will not be degraded. And this protected mRNA that's not degraded. It can therefore be translated into a protein. And, of course, when it's translated into a protein, the final gene product is being made. And so this is a way of turning on the gene and so you can see the off and the on. This is a way of regulating gene expression to turn on or turn off genes. And so this year concludes our introduction to this second level of post transcription allele regulation, and we'll be able to get some practice applying these concepts as we move forward, as well as talk about the third and final level of post transcription regulation, So I'll see you all in that video.

in this video, we're going to talk about the third level of post transcription all regulation and eukaryotes, and that is RNA interference, and so are in a interference. Is commonly abbreviated as just r n A. I with a lower case, I hear, and so RNA interference or are in a I is really just the process of small non coding. RNA is blocking translation of target M RNA molecules. And so these small, non coding RNA yes, are really just short strands of RNA that have a complementary sequence to an M R N a target. And so we'll be able to see more and learn more about them down below in our image. Now, really, there are two possible scenarios that are going to turn gene expression off when it comes to RNA interference. And so the first possible scenario is M. R N A. Is going to be degraded and targeted for degradation. And then the second possible scenario is going to be that the ribosomes is going to be blocked from binding, and that's going to prevent translation. And so let's take a look at our image down below where you can see in our example, RNA interference can block ride his own binding or recruit cellular enzymes for M RNA degradation. And so, over here on the left hand side, notice that we're showing you are miniature version of the map and you can see that again. M RNA degradation and translational control is going to occur in the cytoplasm of the cell outside of the nucleus and so up here, uh, notice in this image where this image we're focusing on RNA interference or are in a I and notice that it's going to require small, non coding RNA s like this little short orange RNA, a molecule that you see at the top. And this short, small, non coding RNA is complementary to a small sequence on the m r N A itself the messenger RNA. And so there are two levels here. There is the M RNA degradation scenario, and then there is the translational control scenario. So in the M RNA degradation scenario, what happens is the small non coding RNA is going to complementary bind to the m r N a. And the mRNA is going to be degraded. It's going to be degraded by enzymes. And so the small, non coding RNA here is basically marking the mRNA for degradation. And so you can see that this enzyme over here is degrading the mRNA into small, tiny pieces. And, of course, the gene product will not be made if the mRNA is being degraded. And so this is a way of turning off the gene expression. Now, if we take a look at the translational control scenario, what happens is the M R N A. The small, non coding RNA complementary binds to the mRNA. But in this scenario, when the small, non coding RNA binds to the m r N a, um, the M r N A is not going to be degraded. Instead, the ribosomes is not going to be able to bind to the m r N A as it normally would to translate it. And so, in this scenario, the ribosomes is blocked from binding to the mRNA. And, of course, that is also going to prevent the gene product, the protein from being made, and so that is also going to be turning off gene expression. And so this here RNA interference is basically interfering with the M r n A and turning off the expression of the M r N A. And so this year concludes our introduction to RNA interference, 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.

in this video, we're going to introduce two different types of small non coding RNA. Yes. And so again, there are two classes of RNA is that are involved in R N A. I or RNA interference. And so the first class is going to be the micro RNA days and the second class are going to be the small interfering RNA Zor for sure, the S I r n A s. And so both types of RNA, the micro R N s and the small interfering RNA s are going to bind to a target mRNA by complementary base pairing. And it's going to turn off expression of a gene through RNA interference. So both micro our knees and small interfering RNA is will turn off expression of a gene. And so what is the difference between the two? Well, the only difference between micro RNA s and S I. R N A s is the structure of their precursor form. And so micro RNA is have a single stranded precursor and s i r N s have a double stranded precursor and so we can take a look at this, uh, in our image down below. And so notice. In this example, we're showing you RNA interference by two types of small non coding. RNA is the micro RNA s and the S I R N s. And so, once again, over here on the far left, we have our miniature version of the map of our lesson. And, uh, notice that RNA interference is really taking place here with M RNA degradation, which is going to occur in the cytoplasm. But it also is going to block translation as well. And so it is a type of translational regulation as well Here and so over here on the left hand side noticed that we're focusing on the micro R N s and the micro RNA is are going to have a single stranded precursor. And so this is the precursor for the micro RNA. And then the micro RNA is going to complementary bind to the m r n a itself and it is going to block transcription. I'm sorry. It's going to block the next step, either mark the molecule for degradation or block the ribs, um, from binding and block translation. And so it is a way of turning off the gene Now, over here on the right hand side, we're focusing on the S I r n s the small interfering RNA s and they have a double stranded precursor. And so notice that up above, we're showing you a double stranded precursor molecule. And so ultimately, it will be converted into its single stranded s i r N A. And it's going to be very, very similar. Under both conditions, they both are going to be complementary, binding to the m r n a. And again it can either mark the M RNA for degradation or it can block the ribosome from translating. And so, in either case, it is going to be interfering with the RNA. It is a type of RNA interference and it will be turning off the genes. And so really, the main learning objective here is that the micro RNA s are going to have single stranded precursors, whereas the S R R N s are going to have double stranded precursors. But other than that, they're going to be very, very similar in their functions. And so this year concludes our introduction to the different types of small non coding RNA s 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.