RNAi may be directed by small interfering RNAs (siRNAs) or microRNAs (miRNAs); how are these similar, and how are they different?

Video transcript

Hi everyone, Welcome back. Let's look at our next question. It says the main distinction between S. I. R. N. A. And M. I. R. N. A. Is that the former is blank or the latter is blank. So let's recall from our continent video first of all what S. I. R. N. A. And M. I. R. N. A. R. And then we have to think about what the main distinction is between them. So we'll start with S. I. R. N. A. Which as we can recall is short interfering RNA. So short interfering RNA, sometimes called silencing RNA is a short sequence of double stranded RNA that enters a cell and forms a silencing conflicts where it unwinds and then it binds to its target. It has a complementary sequence in the cell and at that point that cleaves the M. RNA strand. And then this cell recognizes this foreign S. I. RNA strand, causing the M. RNA to be degraded. That therefore interferes with gene expression because it degrades that M. RNA transcript. The gene does not get expressed as a protein. Now when we look at M. I. R. N. A. M. My RNA is micro RNA. And this micro RNA is a short sequence of RNA that folds back and binds to itself so it has to neighboring sequences that are complementary to each other. This forms a hairpin structure and after formation of a silencing complex similar to the S. I. R. N. A. It then can unwind and bind to a target sequence of R. M. R. N. A. Um And again similar to the S. I. RNA. That causes that target sequence to be degraded. Sometimes it causes it to be translated later. But overall like S. I. RNA. That interferes with gene expression. So with those two things in mind, let's look at our answer choices. Um To decide what is that main distinction between S. I. R. N. A. And M. I. R. N. A. Well the first choice here is choice A. Saying the former S. I. RNA is single stranded while the latter is double stranded. And then we can see that choice B has the same distinction. But in the reverse order saying S. I. RNA is double stranded while M. I. RNA is single stranded. Well this is the main distinction between them. If we look at our description here, we see that S. I. R. N. A. Is a short sequence of double stranded RNA. Whereas micro RNA is a short sequence of RNA that folds back and binds to itself, so it's single stranded that folds binding to itself. So that is the main distinction between them. Both of them are short sequences. Both of them bind to target M. R. N. A. And then both of them cause an interference with gene expression. So the main difference between them is that double stranded versus single stranded. But our answer here is our answer choice B. Because S. I. RNA is double stranded while M. I. RNA is single strand. So Choice B. Is correct. Choice A. Has the distinction between them but in the wrong order. Um Because S. I. RNA is the double stranded one. When we look at choice, see it says that S. Ir nay the former is highly specific while the latter M. I. RNA is less specific. Well this is not correct both of them. The specificity depends on their sequence, not on their structures. So they have a different structure. S. I. RNA being double stranded, M. I. RNA being in these hairpin structures. But again their specificity depends on their base pair complementary binding, which is the same between them. And finally choice D. Says the former S. I. RNA is short in length while the latter M. I. RNA is longer in length. Um And that's not our answer choice because both are similar in length between 20 to 30 bases to over 100 bases. Um Although the S. I. RNA is often a little bit longer than M. I. R. N. A. But compared to that important distinction of double stranded versus single stranded length is not the main distinction between the two of them. So that's why choice D. Is incorrect. So again the main distinction between S. I. R. N. A. And M. I. R. N. A. Is that the former is choice be double stranded while the latter is single stranded. See you in the next video