Question

List three types of alternative splicing patterns and how they lead to the production of different protein isoforms.

Accepted Answer

Hi everyone. Let's look at our next question. It says the most prevalent type of alternative splicing where exxons are excluded from the mature M. RNA is called. So let's look at our answer choices. Well if we don't remember off the top of our head what this form of spicing is. We can actually look at our answer choices and eliminate two of them because we have two things we're looking for. The most prevalent type of alternative spicing. And it's one where Exxon's are excluded from the mature M. R. N. A. Normally you splice out the instructions and leave the exxons of course when we look at our answer choices, we see that choice B is in tron retention. Well as its name as its name suggests intron retention is where you have an in tron included in the mature M. R. N. A. So instead of all the interns being spliced out, one is included. So that's your alternative splicing. So that's not an alternative splicing where Exxon's are excluded. So Choice B is not our answer and enjoy. See is alternative promoters. And this doesn't involve an excellent being excluded although it might happen as a result of this. But an alternative promoter is an alternative form of splicing where the transcription starts in a different site promoter of course is the site where you have RNA preliminaries beginning transcription if you have alternative promoters, there's different sites that result in different mature MRNA. Is that start at different points. So different sites for transcription to begin. So that's not what we're looking for. That's why that's our answer choice. So we're down to two answer choices that involve Exxon's being excluded. And we're looking for the most prevalent type of alternative splicing. And that is choice a cassette. Exxons and cassette exxons. Or where you have an Exxon being left out of the mature M. R. N. A. So you've got your normal spicing where all of the exxons are included after spicing. And then you have an alternative form where what an Exxon is left out at that mature M. RNA. And that is the most prevalent type of alternative splicing. Finally at the choice D. We have mutually exclusive Exxon's um Exxon's do get left out here but instead of just one being left out where you have two forms the one where all the exxons are excluded and one more one is left out. It is slightly different. And I'm just going to put up a little diagram to show. So we look at this diagram we see we have our pre M. R. N. A. With our exxons and introns. And you see in the middle here we have a blue Exxon and a red X. On well are alternatively spliced mature M. RNA. If we look down here is two different versions. One where we have the blue Exxon include but not the red and the other where we have the red Exxon included but not the blue so two mutually exclusive Exxon. So not just to form with all the exxons and one without which is what cassette exon czar, but one where you have these two alternative forms with either or, but that's not the most prevalent form of spicing, so that's not our correct answer. So again, the most prevalent type of alternative splicing where Exxon's are excluded from the mature M. R. N. A. Is called Choice A cassette Exxon's.

List three types of alternative splicing patterns and how they lead to the production of different protein isoforms.

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