Gene Regulation and Expression Quiz
34 Questions
1 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 of the following is NOT a characteristic of regulated genes?

  • They are expressed only under certain conditions.
  • They may be expressed in all cells or only in a subset of cells.
  • Their expression is continually expressed. (correct)
  • Their regulated expression is the basis for cellular differentiation, morphogenesis and adaptability of organisms.

What is the primary function of a promoter sequence?

  • To bind to specific transcription factors (repressors) and inhibit transcription.
  • To bind to RNA polymerase and initiate translation.
  • To serve as binding sites for basal transcription protein factors and RNA polymerase. (correct)
  • To bind to specific transcription factors (activators) and stimulate transcription.

Enhancer sequences are characterized by:

  • Always being close to the promoter sequence.
  • Binding to specific transcription factors (activators) and increasing transcription. (correct)
  • Binding only to RNA polymerase for transcription initiation.
  • Being located only upstream of the +1 position.

What is the main difference between cis-acting and trans-acting elements in gene regulation?

<p>Cis-acting elements are located on the same chromosome as the gene they regulate, while trans-acting elements are encoded by different genes. (A)</p> Signup and view all the answers

What does the term 'constitutive' mean in the context of gene expression?

<p>Genes that are expressed in all cells at a constant level. (A)</p> Signup and view all the answers

Which of the following is an example of a 'regulated' gene?

<p>A gene encoding a protein responsible for producing a specific hormone in response to a signal. (C)</p> Signup and view all the answers

What is the significance of regulated gene expression?

<p>It allows for adaptation to changing environmental conditions and cellular differentiation. (C)</p> Signup and view all the answers

How do 'silencer' sequences differ from 'enhancer' sequences?

<p>Silencer sequences bind to specific transcription factors (repressors) and decrease transcription, while enhancers bind to specific transcription factors (activators) and increase transcription. (B)</p> Signup and view all the answers

What is the role of cAMP in the regulation of gene expression by glucagon?

<p>cAMP activates protein kinase A, which phosphorylates CREB, leading to the activation of genes with CRE in their promoters. (B)</p> Signup and view all the answers

How do steroid hormones regulate gene expression?

<p>Steroid hormones enter the cell and bind to intracellular receptors, forming complexes that activate gene expression. (A)</p> Signup and view all the answers

What is the role of iron regulatory proteins (IRPs) in the regulation of transferrin receptor mRNA stability?

<p>IRPs bind to IRES in transferrin receptor mRNA when iron levels are low, stabilizing the mRNA and increasing transferrin receptor synthesis. (A)</p> Signup and view all the answers

Which of the following is NOT a mechanism of regulation of gene expression at the DNA level in eukaryotes?

<p>RNA splicing and processing. (C)</p> Signup and view all the answers

Give an example of how DNA rearrangements can regulate gene expression.

<p>The production of immunoglobulins by B-lymphocytes through gene rearrangement. (B)</p> Signup and view all the answers

What is the result of the editing of apo B mRNA in intestinal cells?

<p>The creation of a stop codon at codon 2153 (C)</p> Signup and view all the answers

Which of the following accurately describes the proteins produced from apo B mRNA?

<p>Apo B-48 represents only 48% of the apo B-100 protein length. (A)</p> Signup and view all the answers

What type of gene regulation is involved in the differential expression of apo B mRNA in hepatocytes versus intestinal cells?

<p>Posttranscriptional editing (D)</p> Signup and view all the answers

In what way do hepatocytes and intestinal cells differ in processing apo B mRNA?

<p>Intestinal cells perform specific mRNA editing that hepatocytes do not. (B)</p> Signup and view all the answers

What type of modification occurs to the apo B mRNA that alters its final protein product in intestinal cells?

<p>Deamination of cytosine into uracil (A)</p> Signup and view all the answers

What do general (basal) transcription factors specifically recruit during the initiation of transcription?

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

Which type of transcription factors interact with enhancer and silencer DNA sequences?

<p>Specific transcription factors (A)</p> Signup and view all the answers

What is the function of coactivators in gene transcription?

<p>Interact with specific transcription factors (B)</p> Signup and view all the answers

Which epigenetic mechanism is associated with altering DNA structure to make it accessible for transcription?

<p>Chromatin remodeling (B)</p> Signup and view all the answers

How do specific transcription factors modulate the efficiency of transcription initiation?

<p>By interacting with general transcription factors and RNA polymerase (D)</p> Signup and view all the answers

What is the effect of DNA bending during transcription regulation?

<p>Allows interaction between distal regulatory elements and the promoter (A)</p> Signup and view all the answers

Which type of transcription factor is not capable of binding to DNA?

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

What role does histone acetyltransferase (HAT) play in gene regulation?

<p>It facilitates chromatin remodeling by acetylation (C)</p> Signup and view all the answers

What is the process called when chromatin transitions between active and inactive forms?

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

What is the primary difference between euchromatin and heterochromatin?

<p>Euchromatin is associated with active transcription, while heterochromatin is associated with inactive transcription. (D)</p> Signup and view all the answers

What is the effect of histone acetylation on chromatin structure?

<p>It decreases the positive charge of histones, leading to looser DNA wrapping. (A)</p> Signup and view all the answers

How does DNA methylation directly interfere with transcription?

<p>By preventing the binding of transcriptional factors to the promoter region. (A)</p> Signup and view all the answers

Which of the following is TRUE about the relationship between DNA methylation and histone acetylation?

<p>DNA methylation and histone acetylation often work together to repress gene expression. (C)</p> Signup and view all the answers

What is the role of CpG dinucleotides in DNA methylation?

<p>CpG dinucleotides are the primary sites of methylation in vertebrate DNA. (C)</p> Signup and view all the answers

Which of these is TRUE regarding active chromatin?

<p>It is predominantly unmethylated and has high levels of acetylated histone tails. (D)</p> Signup and view all the answers

What is the direct outcome of chromatin remodeling in the context of gene expression?

<p>It controls the accessibility of DNA for transcription. (B)</p> Signup and view all the answers

Flashcards

Constitutive Genes

Genes that are continuously expressed, regardless of environmental conditions. They are essential for basic cellular functions.

Regulated Genes

Genes that are regulated, meaning their expression is controlled and can be turned on or off depending on the needs of the cell or organism.

Cis-Acting Elements

DNA sequences located on the same chromosome as the gene they regulate. These sequences act as 'control knobs' for transcription.

Promoter Sequence

A sequence of DNA located upstream of the transcription start site. It serves as a binding site for RNA polymerase and transcription factors.

Signup and view all the flashcards

Enhancer Sequence

DNA sequences located either upstream or downstream of the transcription start site. They bind specific transcription factors that activate gene expression.

Signup and view all the flashcards

Silencer Sequence

DNA sequences that act like 'brakes' for transcription. They bind specific transcription factors that repress gene expression.

Signup and view all the flashcards

Trans-acting Factors

Proteins encoded by different genes that control the expression of other genes. They bind to cis-acting elements and can either activate or repress transcription.

Signup and view all the flashcards

Transcription

The process of synthesizing RNA from a DNA template. This is the first step in gene expression.

Signup and view all the flashcards

Specific Transcription Factors (TFs)

Proteins that bind to specific DNA sequences, like enhancers and silencers, to regulate gene expression.

Signup and view all the flashcards

General Transcription Factors (TFs)

Proteins that bind to promoter sequences and help recruit RNA polymerase to initiate transcription.

Signup and view all the flashcards

Enhancers

DNA sequences that enhance gene transcription by binding to specific transcription factors.

Signup and view all the flashcards

Silencers

DNA sequences that decrease gene transcription by binding to specific transcription factors.

Signup and view all the flashcards

Coactivators

Proteins that interact with specific transcription factors to regulate gene expression, but do not directly bind to DNA.

Signup and view all the flashcards

Chromatin Remodeling

The process of modifying chromatin structure to make DNA more or less accessible for transcription.

Signup and view all the flashcards

Histone Acetylation

The addition of acetyl groups to histones, a type of protein involved in chromatin structure. This can make DNA more accessible for transcription.

Signup and view all the flashcards

DNA Methylation

The addition of methyl groups to cytosine bases in DNA. This can often decrease gene transcription.

Signup and view all the flashcards

Euchromatin

A relatively relaxed form of chromatin that allows for active transcription. DNA is less tightly packed.

Signup and view all the flashcards

Heterochromatin

A highly condensed form of chromatin that prevents transcription. DNA is tightly packed.

Signup and view all the flashcards

CpG Dinucleotide

A dinucleotide sequence where a cytosine nucleotide is followed by a guanine nucleotide (CpG).

Signup and view all the flashcards

Alternative Splicing

A process where a single gene can produce multiple protein isoforms by altering the splicing pattern of its mRNA transcript. This allows for greater protein diversity and functional complexity.

Signup and view all the flashcards

mRNA Editing

A post-transcriptional modification of mRNA that involves altering the nucleotide sequence, most commonly by converting a cytosine (C) to a uracil (U). This can result in a change in protein sequence and function.

Signup and view all the flashcards

Apo B-100 and Apo B-48

The Apo B gene produces two different proteins, Apo B-100 and Apo B-48. These proteins are important for lipid transport in the body. Apo B-100 is found in VLDLs, while Apo B-48 is found in chylomicrons. The difference in size and function between the two proteins is due to mRNA editing.

Signup and view all the flashcards

Apo B mRNA Editing in the Intestines

mRNA editing occurs in the small intestine, where a specific cytosine base is deaminated to uracil in the Apo B mRNA transcript. This alters the codon sequence from CAA (glutamine) to UAA (stop codon), resulting in the shorter Apo B-48 protein.

Signup and view all the flashcards

Tissue-Specific Apo B Protein Production

Apo B-100, the full-length protein, is synthesized in the liver. Apo B-48, the shorter protein, is synthesized in the small intestine. The difference in the two proteins comes from the presence of a stop codon in the Apo B-48 transcript, resulting from mRNA editing in the intestines.

Signup and view all the flashcards

Cell-surface hormone (e.g., Glucagon)

A type of cell-surface hormone that activates a signaling pathway by binding to its specific receptor. This pathway involves cAMP, protein kinase A, phosphorylation, and activation of CREB, leading to the expression of genes with CRE sequences in their promoters.

Signup and view all the flashcards

Intracellular hormone (e.g., Steroid hormone)

An intracellular hormone, such as a steroid hormone, that directly enters the cell and forms a complex with a receptor protein. This complex binds to a specific DNA sequence, the GRE (glucocorticoid response element), which activates gene expression.

Signup and view all the flashcards

Iron response element (IRE)

A cis-acting element located in mRNA that can bind to the iron regulatory protein (IRP). When iron levels are low, IRP binds to IRES, stabilizing transferrin receptor mRNA and increasing the synthesis of transferrin receptors.

Signup and view all the flashcards

DNA copy number

The number of copies of a specific gene can vary, resulting in different levels of gene expression. This is a mechanism for regulating gene expression, particularly relevant in drug resistance, where gene amplification can lead to increased resistance to a drug.

Signup and view all the flashcards

Study Notes

Course Information

  • Course: BMS 141
  • Lecture Number: 12
  • Title: Regulation of Gene Expression
  • Instructor: Dr. Lamees Dawood
  • Program: Medicine and Surgery
  • Semester: Fall 2024
  • University: Galala University, powered by Arizona State University

Gene Regulation: Different Control Sites

  • Regulation occurs at various levels: Transcription, posttranscriptional processes of mRNA, posttranslational processes, and DNA-related mechanisms in eukaryotes.

Constitutive vs. Regulated Genes

  • Constitutive (Housekeeping) Genes: These genes continuously produce proteins needed for basic cellular functions. They are not regulated.
  • Regulated Genes: These genes are only expressed under specific conditions, such as in certain cells, at a given time, or in response to specific signals (e.g., hormones). This regulated expression is crucial for cellular differentiation, morphogenesis, and adaptability in organisms.

I- At the Level of Transcription

  • Transcription synthesizes RNA.
  • This process is DNA-directed and RNA synthesis is carried out by RNA polymerase.

Glossary: Cis-Acting DNA Sequences

  • Promoter Sequences: Located upstream of the transcription start site (+1 position), acting as binding sites for basal transcription factors and RNA polymerase.
  • Enhancer Sequences: Can be located upstream or downstream or thousands of base pairs away from the transcription start site, acting as binding sites for specific transcription factors (activators).
  • Silencer Sequences: Similar to enhancer sequences but bind to specific transcription factors to repress gene expression (repressors).

Glossary: Trans-Acting Transcription Factors (Protein Factors)

  • General (Basal) Transcription Factors: Protein factors that recognize and bind to promoter sequences, initiating transcription by recruiting RNA polymerase.
  • Specific Transcription Factors: Protein factors that bind to DNA sequences. Activators bind to enhancers and repressors bind to silencers. These factors can regulate transcription in response to signals (e.g., hormones).

1. General or Basal TFs

  • Bind to consensus sequences of the promoter.
  • Important in assembly of the initiation complex and recruitment of RNA polymerase II.
  • Catalyze basal or constitutive transcription.

2. Specific or Regulatory TFs

  • Bind to regulatory sequences (enhancers or silencers).
  • Modulate transcription initiation efficiency.
  • Mediate responses to signals (e.g., hormones).
  • Regulate gene expression at specific times.

Specific or Regulatory TFs Mechanism

  • Specific TFs interact with DNA sequences (enhancers or silencers) through their DNA-binding domain.
  • They interact with general TFs and RNA polymerase at the initiation complex through their protein-binding domain.
  • Coactivator proteins like histone acetyltransferase (HAT) interact via their transcription activation domain.

Bending of DNA Molecule

  • DNA bending allows interactions between specific TFs (bound to enhancer/silencer sequences) and basal TFs and RNAP located at the promoter region.

Regulation of Transcription by Epigenetic Mechanisms (DNA Accessibility)

  • A- Chromatin Remodeling: Acetylation and Deacetylation of histones alter the DNA-histone interaction and influences accessibility.
  • B- DNA Methylation: Alters DNA accessibility by adding methyl groups to cytosines, often within promoter regions. This can either hinder or enhance accessibility during transcription.

Euchromatin and Its Effect on Transcription

  • Following acetylation and nucleosomal removal, the promoter is opened.
  • Transcription machinery can access the promoter, leading to active transcription.

mRNA Posttranscriptional Level Regulation

  • 1. Splice-site choice: Alternative splicing of mRNA molecules (discussed before).
  • 2. mRNA editing: Modifications to mRNA after processing.
  • 3. Coordinate expression: Coordination of gene expression in eukaryotes.
  • 4. mRNA stability: Regulation of mRNA lifespan.

2. The Editing of mRNA

  • Two different-sized Apo B proteins are produced: Apo B-100 (full length, in the liver) and Apo B-48 (smaller, in the intestine).

3. Co-ordinated Expression in Eukaryotes

  • Cell surface hormones like glucagon initiate a signaling pathway involving cAMP, protein kinase A, and CREB.

4. mRNA Stability Regulation

  • Transferrin (an iron transport protein) is regulated via its mRNA stability in response to iron concentration.
  • 1. DNA accessibility: Influenced by chromatin remodeling and DNA methylation to facilitate transcription factors' access to DNA sequences.
  • 2. DNA copy number: Gene amplification affects the amount of DNA.
  • 3. DNA rearrangements: Rearrangement of DNA segments allows for immune responses (immunoglobulins), impacting variety.
  • 4. DNA mobile elements (transposons): Can affect gene expression and have implications in human diseases. DNA rearrangements during immunoglobin creation generates a high diversity of antibodies.

References for Further Readings

  • Lippincott Illustrated Review Integrated System
  • Lippincott Illustrated Review 6th edition
  • Oxford Handbook of Medical Science 2nd edition
  • Clinical Key Student

Studying That Suits You

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

Quiz Team

Related Documents

Regulation of Gene Expression (BMS 141) Lecture Notes Fall 2024 PDF

Description

Test your knowledge on gene regulation and expression with this quiz. Explore topics such as promoter sequences, enhancer and silencer elements, and the role of hormones and proteins in gene expression mechanisms. Perfect for students of molecular biology and genetics.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser