Biology Topic 8 RNA interferance

What is RNA interference? (RNAi)

A form of post - transcriptional gene silencing that occurs in the cytoplasm , where specific mRNA molecules are prevented from being translated, reducing expression of a target gene

Why is RNAi decreibed as sequence - specific?

BEcouse the RNA molecules involved have base sequences complementary to the target mRNA, allownig precise silencing of specific genes

What is the role of RNAi in eukaryotes an dsome prokaryotes?

It inhibits translation from target genes preventing the production of their protines

What are small interfering RNAs (siRNAs)?

Short, double stranded RNA molecules that bind to complementay mRNA from target genes and guid complexes to degrade that mRNA

How do siRNAs silence gene expression?

They bind to complementary mRNA and recruit a protine complex that cuts the mRNA , preventing translation into protines

How is double straded RNA (dsRNA) involved in RNAi?

dsRNA is produced by RNA dependent RNA polymerases and then hydrolysed into siRNAs that initiate the RNA interferance pathway

How are siRNA generated from dsRNA?

dsRNA is hydrolysed into 23 nucleotide fragments , forming siRNAs that can participate in gene slicing

What happens when siRNAs bind to protine complexes in the cytoplasm?

ATP is used to separeat the siRNA strands , exposing bases that can pair with complementary mRNA

How does siRNA recognise its target mRNA?

Through complementary base pairing once the mRNA enters the cytoplasm

What happens to target mRNA once siRNA binds to it?

The assciated protine complex cuts the mRNA into fragments, preventing translation

Why can cut mRNA not be translated?

BEcosue fragmentation disrupts the coding sequence so ribosomes cannot produce a functional protine

What happens to mRNA fragments after cleavage?

Broken down into RNA nucleotides by enzymes in the cytoplasm

How can siRNA be used against viruses?

siRNAs designed to match viral RNA trigger itrs degradtion , preventing the virus from using host machinery to replicate

How can siRNA be used in cancer treatment?

They cna target oncogene mRNA reducing production of protines that drive or maintain cancerous growth