RNA interference (Regulatory Rana's) by CBCS NOTE

What is RNA interference?

What is gene silencing?

RNA interference:

It is a natural phenomenon by which mRNA is silence their by inhibiting the protein coded from that particular mRNA. In this process gene expression is inhibited by RNA molecule by neutralizing the targeted mRNA molecule.

Process: This mechanism is triggered by double stranded RNA, that uses the genes own DNA sequence to turn in off. This process is called gene silencing.It is a gene regulatory mechanism that limits the level of transcript in two ways.

1. Suppressing transcription.(transcriptional gene silence) 
2. Degreding the RNA produced( post
transcriptional gene silence)

The process was discovered by two American Scientist Andrew Z. Fire & Craig C.Mello in the cells of Caenorhabdits Eleglens. They introduced sort segment of Double stranded RNA into the cell of
C.Elegens & Inhibited the expression of certain gene.

Mechanism Of RNA interference: The mechanism of RNA interference Can be explain as follows- 
1) Long double stranded RNA is diest into small fragments with the help of an enzyme called dicer. This small fragments are known as siRNA or small interference RNA. 

2) The siRNA are passed through the RNA induced silencing complex. The duplex unwind RNA degradation & inhibit translation. 
3) The siRNA bind to Agronant protein & one of the strand from the double strand RNA is removed.
The remaining protein either cleaves the mRNA or recruits other factor to regulate target sequence.

Application Of RNA interferences:

1) Gene knockdown: RNA INTERFERENCE is often used to study the function 
of genes in cell culture & in model organism. The mechanism is used to reduced the expression of targeted gene.

2) Functional genomics: It is used for gene maping & annotation in plant. RNA interference has been used for the studies in breed wheat.

3) Application in medicine: With the intervention of synthetically may small interfering RNA. It become possible to silence the specific gene sequence instead of silencing the entire gene. RNA has been used to target specific gene sequence they can caused cancer. It can also be used to treat bacterial diseases, viruses, parasite, relive pain & even modulate sleep.


SiRNA: 1) Short interfering RNA is also known as silencing RNA. It is a class of double stranded RNA molecule. It is 20-25 bp long. It operates within RNA interference pathway by the enzyme diser. It interferes with the expression of specific gene with complementary nucleotide sequences by
degrading mRNA after transcription, reservating no transcription. It repress protein synthesis & regulates the development of organism.

Its application: Testing hypothesis of gene function. Target validation. Pathway analysis. Functional screening. In medicine.

miRNA: It is a non coding RNA molecule of approximately 21-23 nucleotide long & it also inhibit mRNA expression. It is found in plants, animals & some viruses. It functions in RNA silencing & post transcriptional regulation of gene expression. miRNA function through base pairing with
complementary sequence within mRNA molecule. As a result this mRNA molecule are silenced by one or more of following process.

1. Cleavage of the mRNA strand into two peaces.
2. Do stabilizing of the mRNA through shorting of its poly A tail.
3. Less efficient translation of mRNA into proteins by ribosome.

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