Hey everyone. So, in this video, we're going to take a look at the processing of pre-mRNA. Now, with Eukaryotic species, mainly animals and plants, we're going to say DNA contains segments called Exons and Introns. Exons are the portions that code for proteins, while Introns are the portions that do not. Now, with transcription, we're going to say it copies both exons and introns to pre-mRNA, also called hnRNA. You might hear these two terms being used interchangeably. They're the same thing. Now, here, we have a process called processing where spliceosomes are going to process our pre-mRNA to produce mature mRNA for protein synthesis. Now, it cuts the introns out, and it's going to splice the exons together. Our memory tool here is that exons are expressed. If we take a look here at this image, we have our gene, our informational strand. It has exons and introns involved. Through transcription, we still have our exons and introns involved because we're just copying it. This is what we call our pre-mRNA or our hnRNA. Now, this starts to undergo processing. And through processing with our spliceosome, we're cutting the connections between our exons and our introns. And we're going to remove the introns, keeping the exons around. We're going to splice them together. Now we have only exons remaining at the end, and this represents our mature mRNA. Now, recall that when we talk about mRNA, it's going to then move out of the nucleus to the Ribosomes in the Cytoplasm for Protein Synthesis. So, just remember, we're copying a segment of our DNA to make this initial pre-mRNA. It still needs to be processed where we get rid of the introns so that the exons can be expressed later on. This is important so that we are left with what's necessary for proper protein synthesis.
Processing of pre-mRNA - Online Tutor, Practice Problems & Exam Prep
Processing of Pre-mRNA Concept 1
Video transcript
Processing of Pre-mRNA Example 1
Video transcript
Here it says, which of the following statements is incorrect about hRNA, hnRNA processing? Remember, hnRNA is the same thing as pre mRNA. It's the non processed version of mature mRNA. Now, here, hnRNA is processed inside the nucleus in structures called spliceosomes. That's true. Introns that do not code for proteins are removed from hnRNA during processing. That is also true. Spliceosomes join the exons together after introns are removed. Yes, that's correct. Remember, the memory tool: exons are expressed. They're left behind and then spliced together so that they eventually leave the nucleus to go towards the ribosomes, which are in the cytosol for protein synthesis. hnRNA is processed to reduce its size so that it can fit inside ribosomes. Nor did we talk about having to cut out the introns because of spatial issues. It's not about size involved. We're just getting rid of the portions that do not code for proteins. Remember, the whole point of making mRNA is that we can eventually make the necessary proteins from it. So we just gotta get rid of the portions that don't help us code for protein. So here, the answer here would be option d.
The underlined sections of the pre-mRNA below are introns. Write the sequence for mature mRNA.
5’ GCC CGA UUU AUC AGG GAC CCA 3’
5’ GCC UUU AUC AGG 3’
5’ GCC UUU GAC CCA 3’
5’ GCC CGA AUC AGG 3’
5’ GCC CGA UUU CCA 3’