Question

As indicated in the image below, miRNAs usually have imperfect base pairing with their target mRNAs, which leads to translational inhibition (the RISC complex is large, and won't let ribosomes through). On the other hand, siRNAs produced from longer double stranded RNA molecules (e.g. viruses), usually show perfect binding to their target mRNAs, which leads to mRNA degradation by the RISC complex. In 100 words or fewer explain why these two types of inhibitory ncRNAs differ in their mode of action - i.e. why is it that miRNAs usually show imperfect base pairing to their targets, whereas siRNAS usually have perfect matches. (a) MicroRNAS Inverted repeat DNA (b) Small interfering RNAS Double-stranded RNA AGIC 1 Transcription Transcription through an inverted repeat in the DNA... 2 ... produces a primary miRNA (pri-miRNA). Pri-miRNA 1 Double-stranded RNA may arise from RNA viruses or long hairpins. 2 Double-stranded RNA is cleaved by Dicer... Dice 3 The pri-miRNA is. cleaved to produce a short RNA with a hairpin. Cleavage 3 ...to produce SiRNAs. SiRNAS Okos 4 Dicer removes the terminal loop AniRNA caminae

Answer 1

The two small RNAs (siRNA and miRNA) can be differentiated by their origin. si RNA are developed from dsRNA precursors which made up of two distinct perfectly base paired RNA strands whereas miRNA processed from a single, long RNA strand that forms imperfectly base paired hairpin structures. siRNA have recognized as exogenous while miRNA as endogenous origin.