Gene Expression Control in Prokaryotes Part II-D (Exam 2)
44 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which regulatory mechanism is involved in adjusting gene expression in bacteria during transcription?

  • Transcriptional regulation (correct)
  • DNA replication initiation
  • Chromatin remodeling
  • Endonuclease activity

    • What is the role of adenine methylation in bacteria?

  • It facilitates chromatin structure changes.
  • It enhances the transcription of all genes.
  • It protects the chromosome from endonucleases. (correct)
  • It promotes protein synthesis directly.

    • What is the function of orphan methylases at GATC sites?

  • To initiate transcription directly.
  • To enhance operon structure.
  • To regulate gene expression and DNA repair. (correct)
  • To entirely prevent gene expression.

    • How do inducible operons differ from repressible operons?

    <p>Inducible operons are activated by specific substrates.</p> Signup and view all the answers

    What structures in bacteria can modify chromosome architecture?

    <p>NAPs and lncRNAs</p> Signup and view all the answers

    Which statement best describes the regulation of virulence in bacteria?

    <p>It is influenced by transcriptional factors.</p> Signup and view all the answers

    What happens during the generation of positive supercoils in dsDNA?

    <p>It enhances RNA polymerase binding.</p> Signup and view all the answers

    What is the effect of hemimethylation at the dnaA promoter in DNA replication initiation?

    <p>Allows SeqA protein binding.</p> Signup and view all the answers

    What happens to transcription of the operon's structural genes when the product is present in the environment?

    <p>Transcription is inhibited.</p> Signup and view all the answers

    In a repressible operon under positive control, what role does the activator play when it is bound to the promoter?

    <p>It promotes the binding of RNA polymerase.</p> Signup and view all the answers

    What is the outcome when tryptophan concentration is low in the trp operon?

    <p>The repressor is inactive, allowing transcription.</p> Signup and view all the answers

    What initiates the process of attenuation in the trp operon?

    <p>High tryptophan concentration.</p> Signup and view all the answers

    Which molecule directly influences the transcription status in a repressible operon by inactivating the activator?

    <p>Tryptophan.</p> Signup and view all the answers

    How does carbon catabolite repression affect gene expression?

    <p>It prevents transcription of operons when glucose is present.</p> Signup and view all the answers

    What occurs to RNA polymerase when the product is available and the activator is inactivated?

    <p>It can no longer bind to the promoter.</p> Signup and view all the answers

    What is the immediate effect of an active repressor in the trp operon?

    <p>Blockage of transcription.</p> Signup and view all the answers

    What is the role of the substrate in the operon under positive control?

    <p>It assists the activator in facilitating transcription.</p> Signup and view all the answers

    In prokaryotic gene regulation, which level primarily directly affects transcription initiation?

    <p>Transcription level</p> Signup and view all the answers

    What condition will likely result in the transcription being OFF in an inducible operon?

    <p>Substrate absence and repressor binding</p> Signup and view all the answers

    Which genotype is likely to lead to the absence of β-gal when lactose is not present?

    <p>lacI+ lacP+ lacOc lacZ-- lacY+</p> Signup and view all the answers

    Which regulatory feature is NOT involved in transcription regulation in eukaryotes?

    <p>Permissive transcription factors</p> Signup and view all the answers

    What is the possible genotype of an E. coli strain that produces high amounts of ß-galactosidase when grown under conditions inducing the lac operon?

    <p>lacI+ lacP+ lacOc lacZ+ lacY+ lacA+</p> Signup and view all the answers

    Which genotype would likely result in an E. coli strain that does not produce ß-galactosidase under inducing conditions?

    <p>lacI+ lacP– lacO+ lacZ+ lacY+ lacA+</p> Signup and view all the answers

    What would be the consequence of deleting region 1 from the 5’ UTR of the trp operon?

    <p>Decreased transcription caused by loss of regulatory feedback</p> Signup and view all the answers

    Which statement correctly describes the function of a repressor in a negative inducible operon?

    <p>The repressor inhibits transcription in the absence of substrate</p> Signup and view all the answers

    In the context of operons, what role does an activator play in a positive repressible operon?

    <p>It inhibits transcription when the product is present</p> Signup and view all the answers

    What is the main function of an activator in transcriptional regulation?

    <p>To enhance the binding of RNA polymerase to the promoter</p> Signup and view all the answers

    In which mechanism does attenuation occur during transcriptional regulation?

    <p>It causes RNA Pol to pause or terminate transcription</p> Signup and view all the answers

    What condition is necessary for an inducible operon to be active?

    <p>Presence of both the substrate and the activator</p> Signup and view all the answers

    What characterizes a repressible operon?

    <p>It is turned OFF by a product during anabolic processes</p> Signup and view all the answers

    Which process allows RNA polymerase to continue past an initial termination signal?

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

    How do transcription factors function as regulators?

    <p>They can either prevent or facilitate repressor binding</p> Signup and view all the answers

    What does binding of a cofactor to a regulator typically result in?

    <p>Allows the regulator to bind DNA</p> Signup and view all the answers

    What is the role of sigma factors in prokaryotic transcription?

    <p>They initiate binding of RNA polymerase to the promoter</p> Signup and view all the answers

    What is a characteristic of negative control in gene regulation?

    <p>It blocks RNA polymerase from accessing the promoter</p> Signup and view all the answers

    What defines the 'UP element' in transcriptional regulation?

    <p>It enhances the binding of sigma factor and RNA polymerase</p> Signup and view all the answers

    What is the primary effect of an inducible operon when a substrate is present?

    <p>It turns transcription ON.</p> Signup and view all the answers

    Which of the following best describes post-transcriptional regulation?

    <p>Modifications that occur after transcription affecting RNA stability.</p> Signup and view all the answers

    What role do small non-coding RNAs (ncRNAs) primarily play in gene expression?

    <p>They regulate transcription and translation as well as mRNA stability.</p> Signup and view all the answers

    What results from RNA editing, specifically the conversion of adenosine to inosine?

    <p>It changes the codon read by the ribosome.</p> Signup and view all the answers

    Which mechanism is NOT a feature of translational regulation?

    <p>Inhibition of DNA replication.</p> Signup and view all the answers

    In the context of non-coding RNAs, what is a cis-encoded antisense RNA?

    <p>It targets mRNA for degradation and originates near the gene.</p> Signup and view all the answers

    How can RNA turnover be modulated?

    <p>Through the abundance of RNases and binding to ncRNAs.</p> Signup and view all the answers

    What is the consequence of a repressible operon in the presence of a product?

    <p>It turns transcription OFF.</p> Signup and view all the answers

    Study Notes

    Unpopular Opinion on the Greatest Threat to Humanity

    • Humanity's greatest threat is a lack of emotional maturity, ineffective communication, and a lack of empathy when navigating conflict.
    • This leads to internal and interpersonal conflict.
    • Healing is needed to address these issues.

    Control of Gene Expression (Prokaryotes)

    • Gene expression control in bacteria occurs at multiple levels, including:
      • Genome/chromatin structure
      • Epigenetic profile (DNA methylation)
      • Transcriptional regulation
      • Post-transcriptional regulation
      • Regulation of translation
      • Regulation via non-coding RNAs

    Chromatin Structure

    • Nucleoid shape changes due to NAPs (nucleoid-associated proteins) and IncRNAs (long non-coding RNAs).
    • NAPs:
      • Modify chromosome architecture.
      • Mediate interactions with ncRNAs (non-coding RNAs).
      • Regulate transcription by methods such as blocking promoters, facilitating RNAP (RNA polymerase) movement, and altering supercoiling.
      • Regulate virulence and xenogenic silencing.
    • Transcription affects nucleoid structure, requiring available templates and positive supercoils in dsDNA.

    Epigenetic Profile - DNA Methylation

    • Involves adenine methylation, a key component of restriction-modification (R-M) systems.
    • R-M systems protect bacterial chromosomes from their own endonucleases, and also cleave phage DNA.
    • Orphan methylases (GATC sites):
      • Regulate gene expression by allowing the binding of activators or repressors.
      • Enable DNA repair through methyl-directed mismatch repair (MMR) mechanisms.
      • Initiate DNA replication by hemimethylation at the dnaA promoter and oriC, preventing unwanted reinitiation.

    Transcriptional Regulation

    • Bacterial genes are often organized into operons, grouping proteins of the same pathway.
    • Operons facilitate swift responses to environmental changes, enabling bacteria to adapt quickly.
    • Inducible operons: Transcription only occurs in the presence of a substrate.
    • Repressible operons: Transcription is inhibited by a product.

    Post-Transcriptional Regulation

    • RNA editing: rNTPs (ribonucleoside triphosphates) are modified after transcription altering their properties, amino acid sequences, and codon recognition.
    • RNA turnover: Balance between RNA synthesis and degradation, influencing RNA quantity and availability. This is modulated by RNase abundance and location, as well as binding to ncRNAs.

    Regulation of Translation

    • Numerous translational regulation mechanisms overlap with transcriptional regulation.
    • Features of mRNA such as ribosome binding site presence and strength, as well as codon usage bias, are significant.
    • Post-translational editing is also a part of the regulation process.

    Regulation via Non-Coding RNAs

    • Small non-coding RNAs (sncRNAs) are involved in most studied mechanisms.
    • Gene expression regulation involves transcription, translation, and mRNA stability.
    • This includes stress response, virulence, and xenogenic silencing regulation.

    Examples of Regulation via sRNAs

    • Cis-encoded ncRNA elements:
      • Structural motifs in the 5' untranslated region (UTR) respond to cellular or environmental changes.
      • Examples include attenuation, leader peptides, thermosensors, and riboswitches.
    • Cis-encoded antisense RNAs: Target mRNAs for degradation or by forming a duplex with them.
    • Trans-encoded antisense ncRNAs: Affect transcription and translation by targeting mRNAs, located outside the controlling gene's region.

    Riboswitches

    • Transcriptional switches regulated by a molecule's presence or absence.
    • They directly affect the translation process.

    Cis or Trans Encoded Antisense RNAs

    • Cis-encoded: Target mRNA for degradation, in or close to the gene region, produced from an antisense promoter.
    • Trans-encoded: Target mRNA to affect transcription and translation, located in a different genomic locus from the target gene.

    Modes of Transcriptional Regulation

    • Regulatory elements impact the transcription levels.
    • Availability of sigma factor and RNA polymerase.
    • Activator proteins facilitate transcription initiation.
    • Repressor proteins block transcription.
    • Attenuation and Antitermination modify mRNA production.

    Role of Activator and Repressor in Transcription Regulation

    • Activator proteins stimulate transcription.
    • Repressor proteins inhibit transcription.

    Mutation Studies and Merozygotes

    • Study of mutations by observing how these change the expression patterns of genes.
    • Merozygotes (partial diploids): Cells with partial copies of genes on different genetic elements, offering insight into gene function by studying changes in expression patterns.

    Additional Information & Extra Slides

    • Includes specific details about the arginine and maltose operons.

    Application Exercise

    • Determining the function of the different lac operon components based on their genotype and the presence or absence of lactose in the environment.

    Levels of Gene Regulation

    • Regulation occurs at several levels for both prokaryotic and eukaryotic cells, including chromatin, transcription, mRNA processing and stability, translation level, and post-translational modifications.

    Inducible Operon Under Positive Control

    • Substrate and activator work together to activate transcription.
    • Activator aids RNA polymerase binding to the promoter.

    Repressible Operon Under Positive Control

    • Product and activator have opposite effects.
    • Activator aids binding of RNA polymerase to the promoter.

    lac Operon

    • Detailed model of the lac operon, its controlling elements (like CAP sites) and its relation to the expression of lactose-related cellular functions.

    Lactose Absent/Present

    • The lac operon's regulatory genes (lacl, lacP, and laco) are affected by the presence or absence of lactose, affecting the production of various enzymes.

    Carbon Catabolite Repression

    • High glucose levels can repress the lac operon, impacting the expression levels of its components.

    trp Operon

    • Operon controlling tryptophan synthesis, involving attenuation as a mechanism to control gene expression.

    Other Questions (trp operon)

    • Analysis of mutations in the trp operon's regulatory regions.

    Worksheet - Conclusions

    • Summary table of various operon types and their underlying regulatory mechanisms.

    Modes of Transcriptional Regulation (diagram)

    • Diagram summarizing the different modes of transcriptional regulation, indicating the mechanisms and effect.

    Attenuation in trp Operon

    • Details of the attenuation process in the trp operon, showing the role of the ribosome and transcription and its various sequence regions, depending on the tryptophan levels in the environment.

    Low and High Tryptophan Concentration (trp operon)

    • Detailed scenarios explaining the trp operon's regulation mechanisms in response to low and high tryptophan concentrations.

    Other (trp operon) - additional questions

    • Analyzing the effects of deleting regions from the operon.

    Other Questions (general)

    • Understanding when and how a regulator protein binds, and what the consequence of such binding is.

    Additional details about operons and regulatory mechanisms

    • Discusses different types of operons, and the concept of cis and trans regulatory factors.

    Other information

    • Additional information on the operon systems and how operons function in various scenarios.

    Studying That Suits You

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

    Quiz Team

    Related Documents

    Gene Expression Regulation In Prokaryotes PDF

    Description

    This quiz explores the intricate mechanisms involved in the control of gene expression in prokaryotes, particularly bacteria. It covers various levels of regulation, including the roles of genome structure, transcription, and non-coding RNAs. Test your knowledge on how gene expression is finely tuned in these organisms.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser