Question

Briefly describe the role of siRNA and miRNA and suggest why the structure of RNA could play a role in this process.

Answer 1

Small interfering RNA (siRNA ) is a double stranded RNA molecules , 20-25 base pairs in length . It interferes with the expression of specific genes , by degrading mRNA after transcription, preventing translation.

- microRNA or miRNA is a small non-coding RNA molecules. Their main function is they play role in RNA silencing and post-transcriptional regulation of gene expression.

- miRNA resemble the small interfering RNAs (siRNA) of the RNA interfering pathway, except miRNA derive from regions of RNA transcripts that fold back on themselves to form short hairpins,

Whereas siRNA derived from longer regions of double stranded RNA.

- once siRNA enters the cell it get incorporated into other proteins to form the RISC. Once the siRNA is part of RISC complex, the siRNA is unwound to form single stranded siRNA.

- this single stranded siRNA now can scan and find a complementary mRNA. Once single stranded siRNA binds to its target mRNA , it induces mRNA cleavage. So structure and sequence of nucleotide play a major role in binding the complementary strand.

- this cut RNA recognised as abnormal by cell and degradation of mRNA is caused. So no translation of the mRNA into amino acid and then protiens. Thus silencing the gene that encodes mRNA.

Hopefully it helps, thanks.