Gene Regulation and Transcription Factors Quiz
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Questions and Answers

What is the primary function of transcription factors in gene regulation?

  • To directly synthesize mRNA from DNA
  • To influence RNA polymerase's ability to transcribe a gene (correct)
  • To inhibit RNA polymerase from transcribing genes
  • To modify the structure of DNA during transcription

Which type of transcription factors is essential for RNA polymerase to bind to the core promoter?

  • Enhancer transcription factors
  • General transcription factors (correct)
  • Repressor transcription factors
  • Regulatory transcription factors

What aspect of eukaryotic cells does gene regulation contribute to?

  • Uniformity in cell structure and function
  • Reduction in the number of genes required
  • Linear gene expression unaffected by environmental factors
  • The diversity of cell types and functions (correct)

Which of the following correctly describes an activator in gene regulation?

<p>A protein that enhances the binding of RNA polymerase (C)</p> Signup and view all the answers

What transition in transcription do regulatory transcription factors control?

<p>Transition from initiation to elongation (B)</p> Signup and view all the answers

What term describes the influence of multiple factors on gene expression in eukaryotes?

<p>Combinatorial control (C)</p> Signup and view all the answers

Which of the following correctly describes the role of activators in gene transcription?

<p>They stimulate RNA polymerase to initiate transcription. (A)</p> Signup and view all the answers

What is a primary function of repressors in gene regulation in eukaryotes?

<p>Inhibit the ability of RNA polymerase to initiate transcription. (C)</p> Signup and view all the answers

Which of the following influences the activity of activators and repressors in eukaryotic gene regulation?

<p>Binding of small effector molecules and covalent modifications (D)</p> Signup and view all the answers

Where are regulatory elements typically located in relation to the transcriptional start site?

<p>50–100 bp upstream (D)</p> Signup and view all the answers

What is the result of DNA methylation in the context of gene transcription?

<p>It usually inhibits transcription by blocking activator binding. (B)</p> Signup and view all the answers

What type of DNA segments are recognized by regulatory transcription factors?

<p>Regulatory elements (B)</p> Signup and view all the answers

How do eukaryotic genes compare to bacterial genes in terms of organization?

<p>Eukaryotic genes are individually organized, not in operons. (D)</p> Signup and view all the answers

What is the primary role of activator proteins in transcription?

<p>To bind to enhancers and accelerate transcription. (A)</p> Signup and view all the answers

Which element is part of the common features found in eukaryotic protein-encoding gene promoters?

<p>Regulatory elements (C)</p> Signup and view all the answers

How do repressor proteins affect transcription?

<p>They bind to silencers and prevent transcription. (B)</p> Signup and view all the answers

Where is the TATA box generally located in relation to the transcriptional start site?

<p>25 bp upstream of the start site (B)</p> Signup and view all the answers

What effect does the binding of regulatory transcription factors generally have?

<p>It can both enhance and repress transcription. (C)</p> Signup and view all the answers

What determines the precise starting point for transcription?

<p>The TATA box sequence (D)</p> Signup and view all the answers

What are cis-acting elements recognized by regulatory transcription factors?

<p>DNA sequences found in the vicinity of the core promoter (B)</p> Signup and view all the answers

Which of the following is NOT a feature of the common promoter structure in eukaryotic protein-encoding genes?

<p>Ribosome binding site (D)</p> Signup and view all the answers

What happens to eukaryotic gene transcription when enhancers are not functioning?

<p>Transcription levels are very low. (A)</p> Signup and view all the answers

Which regulatory element is responsible for preventing transcription when its expression is not needed?

<p>Silencers (C)</p> Signup and view all the answers

Which term describes regulatory elements that lead to an increase in transcription levels?

<p>Activators (A)</p> Signup and view all the answers

How much can regulatory elements known as activators stimulate transcription?

<p>100-1000 fold (C)</p> Signup and view all the answers

What is the role of regulatory transcription factors in gene transcription?

<p>They can increase or decrease transcription by binding to regulatory elements. (A)</p> Signup and view all the answers

What is the effect of down-regulation in gene transcription?

<p>Decrease in transcription activity (B)</p> Signup and view all the answers

Which of the following statements is true regarding the binding of regulatory transcription factors?

<p>Regulatory transcription factors do not bind directly to RNA polymerase. (A)</p> Signup and view all the answers

What is the primary function of TFIID in transcription?

<p>To recruit RNA polymerase II to the core promoter (D)</p> Signup and view all the answers

How do regulatory transcription factors typically influence RNA polymerase II?

<p>By recruiting coactivators and interacting with TFIID (A)</p> Signup and view all the answers

What role do coactivators play in transcription?

<p>They increase the rate of transcription without binding to DNA (B)</p> Signup and view all the answers

What effect do repressor proteins have on TFIID?

<p>They inhibit TFIID, preventing it from forming a complex with RNA polymerase II (C)</p> Signup and view all the answers

What is the primary purpose of the Mediator complex in transcription?

<p>To facilitate the interaction between RNA polymerase II and regulatory transcription factors (C)</p> Signup and view all the answers

Which proteins facilitate the transition from initiation to elongation in transcription?

<p>Activator proteins through mediator (A)</p> Signup and view all the answers

What does the binding of transcriptional activators to regulatory elements typically do?

<p>Facilitates chromatin accessibility to RNA polymerase (A)</p> Signup and view all the answers

What mechanism do regulatory transcription factors use to influence nucleosome positions?

<p>By recruiting proteins that modify nucleosome positions and compositions (A)</p> Signup and view all the answers

How are regulatory transcription factors typically controlled?

<p>By binding of small effector molecules, protein-protein interactions, and covalent modifications (B)</p> Signup and view all the answers

What is the effect of small effector molecules on regulatory transcription factors?

<p>They promote binding to DNA (C)</p> Signup and view all the answers

In the context of steroid hormones, what is the role of heat shock proteins (HSP)?

<p>They protect the glucocorticoid receptor prior to hormone binding (B)</p> Signup and view all the answers

What happens to the glucocorticoid receptor after binding with its hormone?

<p>It undergoes a structural change exposing its nuclear localization signal (C)</p> Signup and view all the answers

What is a homodimer in the context of glucocorticoid receptors?

<p>Two glucocorticoid receptors that pair up after hormone binding (C)</p> Signup and view all the answers

Where do glucocorticoid receptors travel after forming a homodimer?

<p>Through a nuclear pore into the nucleus (C)</p> Signup and view all the answers

What is the primary function of steroid hormones in relation to gene transcription?

<p>To regulate transcription of specific genes (C)</p> Signup and view all the answers

Which component is crucial for the glucocorticoid receptor to enter the nucleus after hormone binding?

<p>Nuclear localization signal (NLS) (C)</p> Signup and view all the answers

Flashcards

Gene Regulation

The process of controlling the expression of genes, leading to different levels of gene activity.

Transcription Factors

Proteins that influence the ability of RNA polymerase to transcribe a gene.

General Transcription Factors (GTFs)

A group of transcription factors essential for RNA polymerase binding to the core promoter and initiating transcription.

Regulatory Transcription Factors

Transcription factors that control the rate of transcription of specific target genes, acting as regulators.

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Activators

Regulatory transcription factors that increase the rate of transcription of target genes.

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Activator Proteins

Regulatory proteins that bind to specific DNA sequences called enhancers, stimulating the transcription of a specific gene.

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Regulatory Elements

DNA sequences located near the core promoter that influence the rate of transcription.

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TATA Box

A short DNA sequence, usually located about 25 base pairs upstream from the transcriptional start site. It serves as the starting point for transcription.

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Transcriptional Start Site

The specific nucleotide in the DNA where transcription begins.

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Repressor Proteins

Proteins that bind to specific DNA sequences called silencers, preventing the transcription of a specific gene.

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Transcription

The process of creating a messenger RNA (mRNA) molecule from a DNA template.

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Core Promoter

The core promoter is a region in DNA that includes the TATA box and the transcriptional start site. It's where the RNA polymerase binds to initiate transcription.

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Enhancers

Sequences typically found upstream of the core promoter. These sequences are recognized by activator proteins that bind to enhance the transcription of a specific gene.

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Combinatorial Control

In eukaryotes, many different factors work together to regulate gene expression, where the combination of these factors determines the level of gene activity.

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How Activators and Repressors Influence Transcription

The ability of RNA polymerase to initiate transcription is influenced by the interplay of activators and repressors, as well as the state of chromatin.

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Enhancers - Boosting Transcription

Enhancers are DNA segments that increase the rate of transcription, acting as promoters for RNA polymerase.

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DNA Methylation - Transcription Inhibition

DNA methylation involves attaching a methyl group to DNA, typically hindering transcription.

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Regulation of Eukaryotic Protein-Encoding Genes

Eukaryotic protein-encoding genes are regulated by multiple regulatory elements, which are recognized by specific regulatory transcription factors.

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Silencers

Transcriptional regulatory elements that decrease the rate of gene expression by suppressing the ability of RNA polymerase to initiate transcription.

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Up-regulation

The process by which regulatory transcription factors enhance gene transcription.

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Down-regulation

The process by which regulatory transcription factors inhibit gene transcription.

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Indirect binding of regulatory transcription factors

Regulatory transcription factors that do not bind directly to RNA polymerase but instead influence the activity of other factors involved in transcription.

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TFIID

A complex of proteins that binds to the core promoter to initiate transcription.

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What is TFIID?

A protein complex that binds to the TATA box and is essential for recruiting RNA polymerase II to the core promoter.

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What are regulatory transcription factors?

They are proteins that influence the rate of transcription by interacting with other proteins that directly control RNA polymerase II.

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What are coactivators?

These proteins increase the rate of transcription by working with other proteins, but they do not directly bind to DNA.

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What are repressor proteins?

They inhibit the function of TFIID, either by blocking its binding to the TATA box or its ability to recruit RNA polymerase II.

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What is Mediator?

It's a complex of proteins that acts as a bridge between regulatory transcription factors and RNA polymerase II, influencing the progression of transcription.

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How do activators and repressors influence Mediator?

Activators stimulate Mediator to facilitate the switch from initiation to elongation, while repressors have the opposite effect.

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How can regulatory transcription factors affect chromatin?

Regulatory transcription factors can recruit proteins that modify the structure of chromatin, making it more accessible to RNA polymerase.

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What is the role of chromatin remodelers in transcription?

Certain activators recruit proteins that transform chromatin into a more accessible conformation, allowing RNA polymerase to work effectively.

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How are regulatory transcription factors controlled?

Regulatory transcription factors are proteins that control gene expression. They can be regulated in three main ways: by binding small effector molecules, through protein-protein interactions, and by covalent modifications.

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What are steroid hormones?

Steroid hormones are signaling molecules that regulate gene transcription. They diffuse through the cell membrane and bind to specific receptors, ultimately influencing gene expression.

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What is the glucocorticoid receptor?

The glucocorticoid receptor is a protein that binds to glucocorticoid hormones, which are a type of steroid hormone. It acts as a mediator in the regulation of gene expression by these hormones.

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What are HSPs and how do they relate to the glucocorticoid receptor?

Heat shock proteins (HSPs), like HSP90, are chaperone proteins that bind to the glucocorticoid receptor before hormone binding. This association helps maintain the receptor's structure and prevent its premature activation.

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How does the glucocorticoid receptor enter the nucleus?

The glucocorticoid receptor, after binding to its hormone, undergoes a conformational change that exposes a nuclear localization signal (NLS). This signal directs the receptor into the nucleus, where it can influence gene expression.

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What happens to the glucocorticoid receptor before entering the nucleus?

The glucocorticoid receptor forms a dimer, a complex of two identical proteins, before entering the nucleus. This dimerization is crucial for its ability to bind to DNA and regulate transcription.

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What happens to the glucocorticoid receptor dimer in the nucleus?

The glucocorticoid receptor dimer, once inside the nucleus, binds to specific DNA sequences, called glucocorticoid response elements (GREs), to regulate the transcription of target genes.

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What are the effects of glucocorticoid hormones on the body?

Glucocorticoid hormones, through the actions of the glucocorticoid receptor, influence various cellular processes, including nutrient metabolism, immune responses, and stress responses.

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Study Notes

Regulation of Gene Expression in Eukaryotes

  • Gene regulation is the phenomenon where the level of gene expression can vary, ranging from high to low rates.
  • Eukaryotic organisms (protists, fungi, plants, and animals) require gene regulation to control the differences in structure and function of their distinct cell types.
  • Regulatory transcription factors can either activate or inhibit transcription.
  • Nucleosome arrangements and DNA methylation influence transcription, where methylation usually inhibits transcription.
  • Transcription factors are proteins that impact RNA polymerase's ability to transcribe a specific gene.
  • These factors control RNA polymerase's binding to the core promoter region.
  • Transcription factors also regulate the transition from initiation to elongation during transcription.
  • Small RNAs (miRNAs and siRNAs) regulate mRNA translation through RNA interference.
  • mRNA translation can be regulated by proteins that bind to the 5' end of mRNA, impacting mRNA stability.
  • Protein function is influenced by feedback inhibition and covalent modifications.

Two Types of Regulatory Transcription Factors

  • General transcription factors (GTFs) are necessary for the binding of RNA polymerase to the core promoter and its progression to the elongation stage.
  • Regulatory transcription factors control the rate of transcription for specific target genes through various mechanisms.
  • Some regulatory transcription factors influence the ability of RNA polymerase to initiate transcription of a particular gene.
  • These factors bind to cis-acting elements near the core promoter, called regulatory elements.

Eukaryotic Protein-Encoding Genes

  • Eukaryotic protein-encoding genes have three common promoter features: regulatory elements, the TATA box, and the transcriptional start site.
  • The TATA box and transcriptional start site compose the core promoter.
  • The transcription start site designates where transcription begins.
  • The TATA box is typically a 25-base pair sequence (5'-TATAAA-3') upstream of the transcription start site.
  • The TATA box determines transcription's precise starting point within a eukaryotic gene.
  • DNA bending proteins and other enhancer control elements influence gene expression.

Combinatorial Control

  • Eukaryotic genes are regulated independently, not grouped as operons.
  • Numerous factors control most eukaryotic gene expression, termed combinatorial control.
  • Eukaryotic gene regulation shows characteristics similar to those present in bacteria, involving activator and repressor proteins.
  • Activator proteins stimulate RNA polymerase's ability to initiate transcription.
  • Repressor proteins hinder RNA polymerase's initiation ability.
  • The function of activators and repressors can be influenced by small effector molecules, protein-protein interactions, and covalent modifications.
  • Activators modify chromatin structure and DNA methylation typically inhibits transcription.

Regulatory Elements

  • Regulatory elements are DNA segments that control eukaryotic gene expression.
  • Regulatory transcription factors recognize these elements to control RNA polymerase initiating transcription at the core promoter.
  • Enhancers play a crucial role in RNA polymerase's ability to begin transcription and enhance its rate.
  • When enhancers are not functioning, the rate of transcription for most genes is reduced.
  • Silencers prevent gene transcription when it's not needed.

Regulatory Transcription Factors

  • Regulatory transcription factors often do not directly bind to RNA polymerase.
  • These factors commonly influence RNA polymerase II via protein-protein interactions with proteins involved in RNA polymerase II regulation.
  • Regulatory factors modify RNA polymerase II function via the intermediary complexes TFIID and Mediator.
  • TFIID binds to the TATA box, needed for RNA polymerase II recruitment.
  • Mediator integrates signals from various factors and influences RNA polymerase II's ability to proceed from initiation to elongation.

Steroid Hormones

  • Steroid hormones act as signaling molecules synthesized by endocrine glands and secreted into the bloodstream.
  • Hormones influence nutrient metabolism in cells.
  • Hormones enter cell cytosol by diffusing across the plasma membrane.
  • Binding to the receptor causes the release of heat shock proteins
  • The receptor-hormone complex then translocates to the nucleus.

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Related Documents

Lecture 9: Regulation of Gene Expression in Eukaryotes - New Mansoura University PDF

Description

Test your knowledge on the role of transcription factors in gene regulation. This quiz covers essential topics such as RNA polymerase binding, activators, and the significance of gene regulation in eukaryotic cells. Perfect for students studying genetics or molecular biology.

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