miRNA and siRNA Pathways Quiz

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Questions and Answers

What is the role of miRNAs in posttranscriptional gene silencing?

Inhibiting translation of target genes (correct)

Enhancing mRNA transcription

Increasing mRNA halflife

Promoting gene expression

Which protein family plays a central role in RNA silencing processes as essential catalytic components of RISC?

Argonaute (correct)

Ligase

DNA polymerase

Helicase

What is the main function of the Argonaute protein in the RNA-induced silencing complex (RISC)?

Increasing translation efficiency

Enhancing transcription initiation

Blocking translation or cleaving target mRNA (correct)

Promoting mRNA stability

What phenomenon is associated with gene silencing through RNA interference?

Decreased translation efficiency Signup and view all the answers

In Arabidopsis, what happens when there is a mutation in the AGO1 gene, a key component of RISC?

Effector of silencing is not produced, resulting in abnormal development Signup and view all the answers

What is the term coined by researchers to describe the phenomenon of double-stranded RNA (dsRNA) successfully silencing a targeted gene?

RNA interference (RNAi) Signup and view all the answers

What is the similarity between miRNA and siRNA in terms of mRNA cleavage?

Both require perfect complementarity to the mRNA for cleavage Signup and view all the answers

Which molecule is responsible for processing double-stranded RNA (dsRNA) to produce small interfering RNAs (siRNAs) in the RNA interference (RNAi) pathway?

Dicer Signup and view all the answers

In the RNA interference (RNAi) mechanism, which protein manipulates small interfering RNAs (siRNAs) to induce gene silencing?

Argonaute Signup and view all the answers

Which of the following organisms does NOT exhibit post-transcriptional gene silencing (PTGS) through RNA interference (RNAi)?

Saccharomyces cerevisiae (Yeast) Signup and view all the answers

Which type of RNA successfully silenced a targeted gene better than antisense RNA in the experiment mentioned?

Double-stranded RNA (dsRNA) Signup and view all the answers

What is the role of double-stranded RNA (dsRNA) in inducing interference of a mRNA target like Mex-3 in the nematode C.elegans?

It reduces mRNA levels Signup and view all the answers

What is the main role of small interfering RNAs (siRNAs) in gene expression regulation?

Silencing complementary target genes Signup and view all the answers

Which pathway produces microRNAs (miRNAs) that can silence complementary target genes?

MicroRNA pathway Signup and view all the answers

What are the two mechanisms involved in gene silencing by small RNAs?

Transcriptional gene silencing and post-transcriptional gene silencing Signup and view all the answers

Who discovered post-transcriptional gene silencing (PTGS) and in which organism was it first discovered?

R. Jorgensen in plants Signup and view all the answers

Which enzymes of the flavonoid/anthocyanin pathway were involved in the discovery of PTGS in petunia?

CHS and DFR Signup and view all the answers

In the context of RNA interference, what is the function of Dicer?

Producing siRNAs and miRNAs from double-stranded RNA (dsRNA) Signup and view all the answers

Study Notes

Post-transcriptional Gene Silencing

miRNAs play a crucial role in post-transcriptional gene silencing through RNA interference (RNAi)
The Argonaute protein family plays a central role in RNA silencing processes as essential catalytic components of RISC (RNA-induced silencing complex)

RNA-induced Silencing Complex (RISC)

Argonaute protein is the main catalytic component of RISC, responsible for mRNA cleavage
RISC is responsible for recognizing and degrading target mRNA complementary to small RNAs

RNA Interference (RNAi)

RNAi is associated with gene silencing through the degradation of target mRNA
Double-stranded RNA (dsRNA) is responsible for inducing interference of a target mRNA
The term "RNA interference" was coined to describe the phenomenon of dsRNA successfully silencing a targeted gene

MicroRNAs (miRNAs) and Small Interfering RNAs (siRNAs)

Both miRNAs and siRNAs are involved in gene expression regulation through RNAi
miRNAs are processed from hairpin structures, while siRNAs are processed from double-stranded RNA
Both miRNAs and siRNAs induce gene silencing through mRNA cleavage

Processing of double-stranded RNA (dsRNA)

Dicer is responsible for processing dsRNA to produce siRNAs
The RNAi pathway produces miRNAs that can silence complementary target genes

Gene Silencing Mechanisms

Two mechanisms involved in gene silencing by small RNAs are: mRNA cleavage and translation inhibition
PTGS is a mechanism of gene silencing that occurs in many organisms, including plants and animals

Discovery of PTGS

Post-transcriptional gene silencing (PTGS) was first discovered in petunia
The discovery of PTGS involved the silencing of enzymes in the flavonoid/anthocyanin pathway
Andrew Fire and Craig Mello discovered PTGS in the nematode Caenorhabditis elegans (C. elegans)

Organisms exhibiting PTGS

Not all organisms exhibit PTGS through RNAi; Neurospora crassa is an example of an organism that does not exhibit PTGS
PTGS has been observed in many organisms, including plants, animals, and fungi

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Description

Test your knowledge on microRNAs (miRNA) and small interfering RNAs (siRNA) pathways, including their functions in posttranscriptionally repressing target genes. Learn about the Argonaute protein family's role in RNA silencing processes.