One form of posttranscriptional modification of most eukaryotic pre-mRNAs is the addition of a poly-A sequence at the 3' end. The absence of a poly-A sequence leads to rapid degradation of the transcript. Poly-A sequences of various lengths are also added to many bacterial RNA transcripts where, instead of promoting stability, they enhance degradation. In both cases, RNA secondary structures, stabilizing proteins, or degrading enzymes interact with poly-A sequences. Considering the activities of RNAs, what might be general functions of 3'-polyadenylation?

Video transcript

Welcome back. Here's the next problem in poly and ventilation. The enzyme poly a polymerase adds a chain of 100 to 250 adnan nucleotides to the M. RNA molecule? The functions of polyu ventilation include. And then we've got two statements. One and two and their answer choices are various combinations of choice A one is correct and two is incorrect. B both are correct. C. Two is correct and one is incorrect and the none of these. So we need to look at these two statements and just evaluate whether or not they're correct. AH one here says polly ventilation provides stability and prevents degradation. Well, this is true. As we recall, M. R. N. A. Is a lot more likely to degrade than D. N. A. It doesn't have that double helical structure stabilizing it so to keep those M. RNA molecules more stable and lasting longer. The poly A tail provides that function being added on the end preventing degradation through the process of translation. So choice one is true. Then statement to says it exports the mature M. RNA from the nucleus to be translated to protein. This is also true. M. R. And D. M. RNA is produced in the nucleus. But protein translation happens in the cytoplasm. And that poly a tail has a function in sort of helping the guiding the export of M. RNA to get it to the cytoplasm. So both of our statements are correct. So our answer is going to be choice be both one and two are correct and we can therefore eliminate our other options since none of them have both statements being correct. So again, what are the functions of poly ventilation choice be both one and two are correct. Poly ventilation provides stability and prevents degradation, and it explores exports the mature M. RNA from the nucleus to be translated to protein. That was a nice, straightforward one. Hope to see you in the next video.