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?

    <p>Decreased translation efficiency</p> Signup and view all the answers

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

    <p>Effector of silencing is not produced, resulting in abnormal development</p> 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?

    <p>RNA interference (RNAi)</p> Signup and view all the answers

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

    <p>Both require perfect complementarity to the mRNA for cleavage</p> 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?

    <p>Dicer</p> Signup and view all the answers

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

    <p>Argonaute</p> Signup and view all the answers

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

    <p>Saccharomyces cerevisiae (Yeast)</p> Signup and view all the answers

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

    <p>Double-stranded RNA (dsRNA)</p> 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?

    <p>It reduces mRNA levels</p> Signup and view all the answers

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

    <p>Silencing complementary target genes</p> Signup and view all the answers

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

    <p>MicroRNA pathway</p> Signup and view all the answers

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

    <p>Transcriptional gene silencing and post-transcriptional gene silencing</p> Signup and view all the answers

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

    <p>R. Jorgensen in plants</p> Signup and view all the answers

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

    <p>CHS and DFR</p> Signup and view all the answers

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

    <p>Producing siRNAs and miRNAs from double-stranded RNA (dsRNA)</p> 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.

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