Answer
3,1,2,4
Explanation:
Through the mechanism of RNA interference (RNAi), short RNAs can inhibit gene expression. RNAi can function at transcriptional level, translational level, and mRNA stability.
RNAi mechanism has numerous biological functions; it can affect development, for instance in the worm C. elegans, or it can be utilized by plants to evade viral infection.
These short RNAs (abt 23 bp long) also known as siRNAs (short interfering RNAs) are products of long dsRNAs which are cleaved by nuclease Dicer. The siRNAs regulate a nuclease complex called RISC (RN-induced silencing complex) leading to repression of gene expression via three distinct ways;
a) Destroy mRNAs that have complementary sequence with the siRNA
.
b) Inhibit translation of mRNAs that have complementary sequence with the siRNA.
c) Induce chromatin modification within the promoter of these homologous (complementary) genes, thus silencing them.
