Recent

  • Show all results for ""
L5 RNA Mediated Regulation of Gene Expression
40 Questions
1 Views

L5 RNA Mediated Regulation of Gene Expression

Created by
@TimeHonoredLimerick2759

Questions and Answers

What is the approximate length of a precursor miRNA (pre-miRNA)?

  • 60-70 nucleotides (correct)
  • 30-50 nucleotides
  • 100-200 nucleotides
  • 300-400 nucleotides

    • MiRNAs are involved in regulating gene expression in prokaryotic cells.

    False

    What is the role of the RNase III enzyme Drosha in the context of miRNA production?

    Drosha cleaves the stem-loop structure of pri-miRNA to release pre-miRNA.

    The pri-miRNA is processed in the nucleus by a complex that includes Drosha and the double-stranded RNA-binding protein _____ .

    <p>DGCR8</p> Signup and view all the answers

    Match the following components with their roles in miRNA processing:

    <p>Drosha = Cleaves pri-miRNA DGCR8 = Binds to double-stranded RNA Exportin-5 = Exports pre-miRNA to cytoplasm miRNA array = Identifies expressed miRNAs</p> Signup and view all the answers

    What is the primary mechanism by which miRNAs regulate gene expression?

    <p>They bind to mRNA and inhibit translation.</p> Signup and view all the answers

    The number of genes predicted to be regulated by miRNAs in the human genome is significant.

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

    Describe one way RNAi mechanisms have evolved.

    <p>RNAi mechanisms have evolved as a defense against viral infections.</p> Signup and view all the answers

    What is the primary function of Drosha in the RNA interference (RNAi) pathway?

    <p>Cleaves pre-miRNA at a specific site</p> Signup and view all the answers

    Dicer contains only one RNase III domain.

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

    Name the two primary reasons for the evolution of RNAi mechanisms.

    <p>To protect the genome from transposable elements and to provide a defense against viral infections.</p> Signup and view all the answers

    The enzyme that degrades RNA is called ____.

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

    Which structural class does Dicer belong to?

    <p>Class III</p> Signup and view all the answers

    Match the following components of miRNA processing with their functions:

    <p>Drosha = Cleaves pre-miRNA Dicer = Cuts dsRNA to create miRNA duplex RNase = Degrades RNA Argonaute = Binds miRNA to target mRNA</p> Signup and view all the answers

    Humans have multiple copies of both Dicer and Drosha.

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

    How can miRNAs be identified using sequencing?

    <p>By purifying miRNA from total RNA, annealing adaptors, and using reverse transcriptase to synthesize DNA.</p> Signup and view all the answers

    What is the primary purpose of using PCR in the context of miRNA?

    <p>To amplify single stranded DNA product of reverse transcription</p> Signup and view all the answers

    Over 60% of human genes are predicted to be regulated by microRNAs.

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

    What common diseases have been associated with mutations in microRNA sequences?

    <p>Hearing loss, keratoconus, and cataract.</p> Signup and view all the answers

    The human genome is thought to encode over _____ microRNAs.

    <p>2000</p> Signup and view all the answers

    Match the type of disease with its associated microRNA mutation:

    <p>miR-96 = Hearing loss miR-184 = Keratoconus and cataract Dysregulated miRNAs = Cancer Common miRNA function = Gene regulation</p> Signup and view all the answers

    Which of the following best describes the function of miRNAs in biological processes?

    <p>They regulate the expression of genes.</p> Signup and view all the answers

    MiRNAs are often found to be DOWNREGULATED in cancer.

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

    How has RNA interference (RNAi) been used in generating mutant phenotypes?

    <p>RNAi has been used to silence specific genes, leading to novel mutant phenotypes by impairing gene expression.</p> Signup and view all the answers

    What is the primary role of the dicer enzyme in miRNA processing?

    <p>It cleaves the terminal loop of the pre-miRNA.</p> Signup and view all the answers

    The mature RISC complex contains both the guide and passenger strands of the miRNA.

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

    Name one mechanism by which miRNA regulates gene expression.

    <p>Deadenylation and degradation</p> Signup and view all the answers

    The guide strand typically binds to the _____ region of its target mRNA.

    <p>3’ untranslated</p> Signup and view all the answers

    Match the mechanism of miRNA regulation with its description:

    <p>Deadenylation = Removal of the polyA tail and subsequent degradation Translation inhibition = Argonaute prevents ribosome binding Endonucleolytic cleavage = Direct cuts in target mRNA strands Stimulation of translation = Rarer mechanism where translation is enhanced</p> Signup and view all the answers

    What typically happens to the mRNA after the binding of the miRNA in mammals?

    <p>The mRNA can either be degraded or have its translation inhibited.</p> Signup and view all the answers

    MiRNA functions only at the transcriptional level in eukaryotic cells.

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

    What specific type of RNA do RNase III family members target?

    <p>Double-stranded RNA</p> Signup and view all the answers

    What is the primary purpose of using RNAi in C.elegans research?

    <p>To identify genes involved in various biological processes</p> Signup and view all the answers

    The sense strand and antisense strand are both produced from the gene insert in RNAi studies.

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

    What organism is commonly used in RNAi research for fat regulation and obesity gene identification?

    <p>C.elegans</p> Signup and view all the answers

    SiRNA stands for _____________________.

    <p>small interfering RNA</p> Signup and view all the answers

    Match the following RNAi delivery methods with their descriptions:

    <p>Chemically synthesized siRNA = Delivered via multiple techniques Engineered viruses = Generate siRNA by transcription Nanoparticles = Surround siRNA with lipid for cellular entry Endocytosis = Process by which cells intake siRNA</p> Signup and view all the answers

    What is the length of small interfering RNA (siRNA)?

    <p>20-25 base pairs</p> Signup and view all the answers

    C.elegans has been shown to have no fat regulatory genes previously implicated in fat storage.

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

    What is one way RNAi could be used therapeutically?

    <p>To treat human disease or infection</p> Signup and view all the answers

    Study Notes

    Origin and Mechanism of MicroRNAs (miRNAs)

    • MicroRNAs are small, non-coding RNA molecules produced from genomic DNA in eukaryotic cells.
    • Primary miRNAs (pri-miRNAs) are regulated by transcription factors, often exceeding 1000 nucleotides in length, potentially producing multiple miRNAs.
    • The microprocessor complex, comprising the RNase III enzyme Drosha and DGCR8, processes pri-miRNAs in the nucleus by cleaving their stem-loop structure to form precursor miRNAs (pre-miRNAs).
    • Pre-miRNAs, approximately 60-70 nucleotides long, are exported to the cytoplasm by Exportin-5, utilizing GTP-Ran.
    • Dicer cleaves the terminal loop of pre-miRNA, yielding miRNA:miRNA duplexes (21-25 nucleotides).
    • The guide strand (antisense) is incorporated into the RISC (RNA-induced silencing complex) alongside Argonaute, while the passenger strand is discarded.
    • Mature RISC modulates gene expression, primarily binding to the 3’ untranslated region (3’UTR) of target mRNAs, often with partial complementarity.

    Regulation of Gene Expression by miRNAs

    • RNA interference (RNAi) silences gene expression both transcriptionally and post-transcriptionally.
    • Regulatory RNAs target mRNAs through complementary base pairing, leading to mRNA degradation or translation blockage.
    • Some regulatory RNAs can repress gene transcription in the nucleus by altering chromatin structure.
    • Mechanisms of miRNA-mediated regulation include:
      • Endonucleolytic cleavage of target mRNA.
      • Deadenylation (removal of polyA tail) leading to degradation.
      • Inhibition of translation initiation by preventing ribosome binding.
      • Inhibition after translation initiation resulting in loss of protein production.

    Structure and Function of RNase III Family Members

    • RNase III family members are nucleases specific to double-stranded RNA.
    • Common structural motifs include:
      • Class I (prokaryotic) with one RNase III domain and one double-stranded RNA-binding domain.
      • Class II (eukaryotic, e.g., Drosha) with two RNase III domains and one dsRNA-binding domain, cleaving 11 bases from stem-loop junctions.
      • Class III (eukaryotic, e.g., Dicer) features two RNase III domains, one dsRNA-binding domain, and a PAZ domain, crucial for processing pre-miRNA.

    Evolution of RNAi Mechanisms

    • RNAi mechanisms likely evolved to protect genomes against transposable elements, safeguarding gene function.
    • They also offer defense against viral infections by silencing viral RNAs, evidenced by increased susceptibility of argonaute mutants in plants to viruses.

    Identification of miRNAs

    • MiRNA sequencing involves purifying miRNA from total RNA through size selection and attaching adaptors for reverse transcription to create complementary DNA.
    • PCR amplifies the reverse transcription product, generating double-stranded DNA indicative of miRNA sequence.
    • MiRNA arrays utilize synthetic oligonucleotides to detect mature miRNAs by hybridization and fluorescence quantification.

    Expression and Regulation of miRNAs

    • The human genome encodes over 2000 miRNAs, with at least 60% of genes predicted to be regulated by miRNAs.
    • MiRNAs play a crucial role in multiple biological processes and are implicated in various diseases, including cancer.
    • Changes in miRNA expression or mutations can lead to diseases such as hereditary progressive hearing loss (miR-96) and keratoconus (miR-184).
    • Dysregulation of miRNAs is frequently observed in cancer, often resulting in downregulation.

    Utilizing RNAi in C. elegans Research

    • Researchers employ RNAi in C. elegans to silence individual genes systematically, elucidating gene functions related to processes like fat regulation.
    • Methods include cloning genes into plasmids for transformation into E. coli or directly injecting double-stranded RNA into nematodes.

    Therapeutic Applications of RNAi

    • RNAi strategies can target disease-related genes (e.g., obesity) identified through research in model organisms like C. elegans.
    • Therapeutic approaches include:
      • Delivery of chemically synthesized small interfering RNAs (siRNAs) via various methods.
      • Engineer viruses to transcribe siRNA in targeted cells.
    • Nanoparticles can facilitate siRNA delivery, allowing entry into cells through endocytosis, where they bind to Argonaute to exert their effects.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz explores the origins and mechanisms of micro RNA (miRNA) production in eukaryotic cells. It covers the regulatory roles of miRNAs in gene expression, the domain structure of RNase III family members, and methods for identifying miRNAs using arrays and sequencing. Test your understanding of these crucial molecular processes.

    More Quizzes Like This

    MicroRNA Biogenesis Quiz
    30 questions

    MicroRNA Biogenesis Quiz

    UnboundChrysoprase avatar
    UnboundChrysoprase
    MicroRNA (miRNA) Basics
    3 questions

    MicroRNA (miRNA) Basics

    DextrousHeliotrope8669 avatar
    DextrousHeliotrope8669
    RNA Mediated Regulation
    30 questions

    RNA Mediated Regulation

    SharpChalcedony avatar
    SharpChalcedony
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser