Gene Expression
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Questions and Answers

The process of regulating the assembly of transcription-initiation complexes involves ______ and repressors.

activators

Albumin is produced by the ______ and functions to regulate osmotic pressure.

liver

Micro RNA, or ______, is a type of RNA interference that can lead to mRNA degradation.

miRNA

Proteins targeted for degradation are tagged with ______ before being broken down in the proteosome.

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

Cytoplasmic determinants, found in the egg's ______, significantly impact embryonic development.

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

Bicoid mRNA is located at the far ______ end of a mature egg.

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

Fertilization leads to the translation of bicoid mRNA into ______.

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

Bicoid protein diffuses from the anterior to the ______ of the embryo.

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

In the 1940s, Edward Lewis mapped mutations to specific ______.

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

Homeotic genes control pattern formation in the late embryo, larva, and ______.

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

Mutations in homeotic genes can cause body segments to develop ______.

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

Wild type individuals exhibit normal ______ development.

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

Humans possess homeotic or ______ genes that regulate development.

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

The ______ model of gene regulation was discovered in 1961 by Jacob and Monod.

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

In eukaryotes, gene regulation involves factors such as histone modifications and ______ methylation.

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

The ______ operon is an example of a repressible operon.

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

Histone acetylation adds acetyl groups to histones, altering the ______ of chromatin.

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

Sections of DNA that are non-coding to which transcription factors bind are known as ______ elements.

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

Activators and repressors can regulate changes in ______ structure.

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

MRNA degradation is one of the ways that eukaryotes control ______ expression.

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

The lac operon is characterized as an ______ operon.

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

Signals that cause changes in a target cell is called ______.

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

The earliest changes in a cell are observed at the ______ level.

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

Determination is followed by ______.

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

Cytoplasmic ______ provide positional information for axes in an unfertilized egg.

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

The bicoid gene codes for a ______ protein involved in specifying the anterior end of the embryo.

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

The development from egg to larva includes several stages, starting with the ______ egg.

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

The segments of the body in the embryo begin to form during early ______.

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

Changes at the molecular level drive the ______ process that leads to observable changes in cell identity.

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

______ cells provide support and nutrients to the developing egg cell.

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

An embryo with two mutant alleles of the bicoid gene may have ______ halves of its body.

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

The highly cooperative assembly of initiation complexes generally requires several ______.

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

Cytoplasmic determinants in the egg's cytoplasm include RNA and ______.

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

Ubiquitin tags proteins for ______ in the proteosome.

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

Signal transduction pathways involve communication where one group of cells influences another group during ______.

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

Alternative splicing leads to the production of multiple ______ from a single gene.

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

The _____ model of gene regulation explains how genes can be regulated in prokaryotes.

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

In eukaryotes, _____ modifications can affect the structure of chromatin and thus regulate gene expression.

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

DNA _____ is a process that involves adding methyl groups to DNA, typically occurring at cytosine bases.

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

Specific _____ factors bind to control elements on DNA to regulate gene transcription.

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

The lac operon is an example of an _____ operon that is regulated by the presence of lactose.

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

One way eukaryotes control gene expression is through _____ splicing, which allows for multiple protein variants from a single gene.

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

In gene regulation, activators are proteins that _____ transcription, while repressors inhibit it.

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

The binding of transcription factors to _____ elements can lead to increased or decreased gene expression.

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

Bicoid protein creates a concentration ______ in the embryo.

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

Homeotic genes are responsible for regulating anatomical ______.

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

Edward Lewis made significant contributions to genetic mapping in the ______.

<p>1940s</p> Signup and view all the answers

Mutations in homeotic genes can lead to ______ development of body segments.

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

In mature eggs, Bicoid mRNA is localized at the far anterior ______.

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

The homeotic gene Antennapedia causes ______ instead of normal antennae.

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

Bicoid mRNA is translated into ______ during fertilization.

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

The bicoid gene is critical for specifying the ______ end of the embryo.

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

The ______ changes set a cell on a path of specialization.

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

Cytoplasmic determinants and inductive signals contribute to the development of ______ organization.

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

Molecular cues tell a cell its location relative to the body ______ and neighboring cells.

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

Egg polarity genes are responsible for synthesizing ______ determinants.

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

The bicoid gene codes for a ______ protein that is involved in specifying the anterior end of the embryo.

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

The earliest changes in embryonic development are observed at the ______ level.

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

An embryo with two mutant alleles of the bicoid gene may lack the front half of the body and have two ______.

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

What is the primary function of cytoplasmic determinants in embryonic development?

<p>To provide positional information for body axes</p> Signup and view all the answers

Which type of RNA is primarily involved in leading to mRNA degradation?

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

What is the role of ubiquitin in protein regulation?

<p>To tag proteins for degradation</p> Signup and view all the answers

How do signal transduction pathways affect embryonic development?

<p>By influencing one group of cells to affect another</p> Signup and view all the answers

Which of the following is true regarding activators in gene transcription?

<p>They enhance the initiation of transcription</p> Signup and view all the answers

Which is a characteristic of the operon model in prokaryotes?

<p>Genes are expressed together or not at all.</p> Signup and view all the answers

What role do proximal control elements play in eukaryotic gene regulation?

<p>They bind transcription factors to facilitate or inhibit transcription.</p> Signup and view all the answers

What is the effect of histone acetylation on gene expression?

<p>It promotes gene expression by loosening chromatin.</p> Signup and view all the answers

Which of the following describes the function of enhancers in gene regulation?

<p>They increase gene expression by binding activator proteins.</p> Signup and view all the answers

In eukaryotes, how does DNA methylation typically affect gene expression?

<p>It leads to silencing of genes, especially when methyl groups are added to CpG dinucleotides.</p> Signup and view all the answers

What is the primary role of specific transcription factors in gene regulation?

<p>They modify histones to alter chromatin structure.</p> Signup and view all the answers

What is the significance of the trp operon in bacterial gene regulation?

<p>It regulates the synthesis of tryptophan and is a repressible operon.</p> Signup and view all the answers

Which process is NOT involved in the regulation of gene expression in eukaryotes?

<p>Operon regulation</p> Signup and view all the answers

What role does Bicoid protein play during embryonic development?

<p>It specifies the anterior end of the embryo.</p> Signup and view all the answers

What occurs after the fertilization of an egg with regard to Bicoid mRNA?

<p>Bicoid mRNA is translated into protein.</p> Signup and view all the answers

Which of the following best describes homeotic genes?

<p>They control pattern formation and anatomical structures.</p> Signup and view all the answers

What observable phenotype results from a mutation in homeotic genes such as Antennapedia?

<p>Growth of legs instead of antennae.</p> Signup and view all the answers

How does Bicoid protein influence the embryo after its translation?

<p>It creates a concentration gradient from anterior to posterior.</p> Signup and view all the answers

What significant insight did Edward Lewis contribute to genetic studies?

<p>Mapping mutations to specific homeotic genes.</p> Signup and view all the answers

What are nurse cells responsible for in the context of egg development?

<p>Providing nutrients and support to the developing egg cell.</p> Signup and view all the answers

The concentration gradient created by Bicoid protein is crucial for which aspect of embryonic development?

<p>Establishing anterior-posterior polarity.</p> Signup and view all the answers

What is the primary role of inductive signals in cell development?

<p>To induce changes in target cell fate and function</p> Signup and view all the answers

What is the significance of cytoplasmic determinants in embryonic development?

<p>They provide spatial information for axes in the unfertilized egg</p> Signup and view all the answers

Which stage follows determination in the cell specialization process?

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

What happens to an embryo with mutations in both alleles of the bicoid gene?

<p>It develops with two tails and lacks the front half</p> Signup and view all the answers

What is characterized by visible changes in cell identity that occur after determination?

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

How do cytoplasmic determinants affect embryonic axis formation?

<p>They provide positional information relative to body axes</p> Signup and view all the answers

What initiates the process of body segmentation in the early embryo?

<p>Cytoplasmic determinants and inductive signals</p> Signup and view all the answers

What does determination primarily lead to in embryonic cells?

<p>Irreversible commitment to a specific fate</p> Signup and view all the answers

Which factor significantly contributes to the spatial organization during embryonic development?

<p>Cytoplasmic determinants and inductive signals</p> Signup and view all the answers

What is a primary factor in determining the anterior end of an embryo?

<p>Bicoid protein concentration</p> Signup and view all the answers

What role do cytoplasmic determinants play in early embryonic development?

<p>They impact embryonic development by influencing positional information.</p> Signup and view all the answers

Which process leads to mRNA degradation or translation inhibition?

<p>RNA interference through miRNA or siRNA</p> Signup and view all the answers

How do activators and repressors influence gene expression?

<p>By regulating the assembly and initiation of transcription complexes.</p> Signup and view all the answers

What is the primary function of albumin in the bloodstream?

<p>To regulate osmotic pressure within blood cells.</p> Signup and view all the answers

What is the overall consequence of differential gene expression during embryonic development?

<p>It leads to the formation of a diverse range of cell types.</p> Signup and view all the answers

Which mechanism enables eukaryotic cells to produce different cell types from the same genetic material?

<p>Alternative RNA splicing</p> Signup and view all the answers

Which of the following is NOT a way eukaryotic cells regulate gene expression?

<p>Operon model transcription</p> Signup and view all the answers

What is the function of distal control elements in eukaryotic gene regulation?

<p>They group together to form enhancers.</p> Signup and view all the answers

In the context of the trp operon, what happens when tryptophan levels are high?

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

What are transcription factors, and how do they influence gene expression?

<p>They bind to control elements and regulate chromatin structure.</p> Signup and view all the answers

Which type of modification directly impacts the accessibility of DNA for transcription in eukaryotic cells?

<p>Histone acetylation</p> Signup and view all the answers

When histones undergo methylation, how does it generally affect gene expression?

<p>It can suppress gene expression.</p> Signup and view all the answers

In what manner do activators and repressors influence transcriptional activity?

<p>Both activators and repressors alter chromatin structure and histone modifications.</p> Signup and view all the answers

What is the primary role of homeotic genes in organismal development?

<p>They determine the specific sites of anatomical structure development.</p> Signup and view all the answers

What result occurs from a mutation in homeotic genes like Antennapedia?

<p>Body segments may develop abnormally.</p> Signup and view all the answers

How does Bicoid mRNA contribute to embryonic development?

<p>It establishes a concentration gradient for anterior-posterior axis determination.</p> Signup and view all the answers

Edward Lewis's work in the 1940s was pivotal for identifying which genetic aspect?

<p>The mapping of mutations to specific genes.</p> Signup and view all the answers

What happens to Bicoid protein after fertilization?

<p>It diffuses from the anterior to the posterior end of the embryo.</p> Signup and view all the answers

In the context of embryonic development, what is the role of nurse cells?

<p>They provide nutrients and support to the developing egg cell.</p> Signup and view all the answers

What is the primary feature of bicoid mRNA localization within the egg?

<p>It is localized at the far anterior end to dictate anterior development.</p> Signup and view all the answers

What kind of gradient does Bicoid protein create during early embryonic development?

<p>A concentration gradient essential for cell differentiation.</p> Signup and view all the answers

What is the process that follows determination in embryonic development?

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

What initiates changes in a target cell during the induction process?

<p>Growth factors</p> Signup and view all the answers

How does molecular change contribute to cell specialization?

<p>By altering protein synthesis rates</p> Signup and view all the answers

Which statement about the bicoid gene is correct?

<p>It codes for a morphogen involved in anterior specification.</p> Signup and view all the answers

What is meant by 'determination' in the context of embryonic cells?

<p>Irreversible commitment to a cell fate</p> Signup and view all the answers

Which of the following best describes the pattern formation in embryos?

<p>It begins during early embryonic development.</p> Signup and view all the answers

What is the primary function of the nurse cells in the ovarian follicle?

<p>Providing support and nutrients to developing eggs</p> Signup and view all the answers

How does the presence of maternal effect genes influence embryonic development?

<p>They synthesize morphogens influencing body axes.</p> Signup and view all the answers

What happens to an embryo with two mutant alleles of the bicoid gene?

<p>It may lack the posterior end, presenting as having two tails.</p> Signup and view all the answers

What is the primary function of albumin in the body?

<p>To regulate osmotic pressure in blood cells</p> Signup and view all the answers

What role do activators play in transcription?

<p>They regulate the assembly of transcription-initiation complexes.</p> Signup and view all the answers

How do miRNA and siRNA primarily function in gene regulation?

<p>By leading to mRNA degradation or inhibition of translation</p> Signup and view all the answers

What is the result of differential gene expression during embryonic development?

<p>Variable development of different cell types</p> Signup and view all the answers

What is the significance of signal transduction pathways in embryonic development?

<p>They allow communication between different embryonic cells.</p> Signup and view all the answers

What is the primary function of the operon model?

<p>To regulate gene expression in response to environmental changes.</p> Signup and view all the answers

Which of the following describes histone acetylation?

<p>Covalent attachment of acetyl groups to histones.</p> Signup and view all the answers

What do specific transcription factors do?

<p>Bind to control elements to regulate gene expression.</p> Signup and view all the answers

How does DNA methylation typically affect gene expression?

<p>It often silences gene expression.</p> Signup and view all the answers

What role do enhancers play in gene regulation?

<p>They help increase gene expression when transcription factors bind.</p> Signup and view all the answers

What characterizes the trp operon?

<p>It is a repressible operon that is inhibited by tryptophan.</p> Signup and view all the answers

What is one effect of alternative RNA splicing?

<p>It generates multiple protein variants from a single gene.</p> Signup and view all the answers

What impact does the binding of activators have on chromatin?

<p>They lead to changes in chromatin structure that enhance transcription.</p> Signup and view all the answers

What role do homeotic genes play in embryonic development?

<p>They control the development of body segments.</p> Signup and view all the answers

What is the function of Bicoid protein in the embryo?

<p>To create a concentration gradient that influences anterior-posterior axis formation.</p> Signup and view all the answers

What effect do mutations in homeotic genes have on an organism?

<p>They can lead to abnormal development of body segments.</p> Signup and view all the answers

What process occurs following the fertilization of an egg with regard to Bicoid mRNA?

<p>Bicoid mRNA is translated into Bicoid protein.</p> Signup and view all the answers

How did Edward Lewis contribute to the understanding of genetics?

<p>He mapped mutations to specific homeotic genes.</p> Signup and view all the answers

Where is Bicoid mRNA located within a mature egg?

<p>At the far anterior end.</p> Signup and view all the answers

What is a characteristic feature of wild type individuals compared to mutants?

<p>They exhibit standard anatomical structures.</p> Signup and view all the answers

Which of the following describes the action of nurse cells during embryonic development?

<p>They provide nourishment and support to the developing egg.</p> Signup and view all the answers

What is the initial stage observed during the determination process of a cell?

<p>Molecular changes</p> Signup and view all the answers

What describes the process that leads to a cell becoming irreversibly committed to its final fate?

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

Which process follows determination in the development of a cell?

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

What are signals that influence nearby cells in the context of cell development called?

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

What kind of information do cytoplasmic determinants provide to a developing embryo?

<p>Positional information</p> Signup and view all the answers

What is the function of the bicoid gene in embryonic development?

<p>To specify body polarity</p> Signup and view all the answers

Which of the following best describes the role of inductive signals in early embryonic development?

<p>They shape body axes and organization.</p> Signup and view all the answers

How does a larva develop from an egg according to the stages mentioned?

<p>Through several distinct stages</p> Signup and view all the answers

What outcome may occur in a larva with two mutant alleles of the bicoid gene?

<p>It lacks the front half of the body.</p> Signup and view all the answers

What is one effect of cytoplasmic determinants on a developing organism?

<p>They influence the spatial organization of cells.</p> Signup and view all the answers

Study Notes

Gene Expression Regulation

  • Prokaryotic genes are organized into operons, clusters of genes under the control of a single promoter
  • Eukaryotes use multiple mechanisms to regulate gene expression, including chromatin structure, DNA methylation, specific transcription factors, alternative RNA splicing, mRNA degradation, and protein degradation
  • Multicellular organisms exhibit differential gene expression, meaning different genes are active in different cell types. This is guided by maternal effect genes and environmental cues, leading to cell differentiation and pattern formation
  • Defects in gene regulation can cause malformations and diseases like cancer

Learning Objectives

  • Understanding how bacteria regulate gene expression in response to environmental changes
  • Understanding how eukaryotes regulate gene expression to create different cell types

Regulation of a Metabolic Pathway

  • Gene expression and enzyme activity regulation are involved in controlling metabolic pathways.
  • Long-term control involves regulating gene expression.
  • Short-term control involves regulating enzyme activity.

The Operon Model

  • Discovered by Jacob and Monod (1961)
  • A functioning unit of genomic DNA controlling a cluster of genes
  • Genes are transcribed together into mRNA and translated together in the cytoplasm
  • Genes in the operon are either expressed together or not at all.
  • Multiple genes need to be co-transcribed to define an operon, including a regulatory gene, promoter, operator, and structural genes.

trp Operon (Repressible)

  • DNA has regulatory gene (trpR)
  • RNA polymerase binds to the promoter when tryptophan is absent, initiating the transcription of genes in the operon
  • When tryptophan is present, it acts as a corepressor, activating the repressor protein, which binds to the operator and stops transcription

lac Operon (Inducible)

  • DNA has the regulatory gene (laci)
  • When lactose is absent, the repressor protein is active, preventing RNA polymerase from binding to the promoter. Therefore, the operon is OFF.
  • When lactose is present (inducer), it binds to the repressor, inactivating it. RNA polymerase can now bind to the promoter causing transcription of the operon, and the operon is ON.

Gene Regulation in Eukaryotes

  • Chromatin Structure: Histone modifications (acetylation and methylation) influence DNA accessibility, impacting gene expression.
    • Acetylation usually makes DNA accessible.
    • Methylation typically makes DNA inaccessible.
  • DNA Methylation: Covalent attachment of methyl groups (CH3) to cytosine bases, typically at CpG dinucleotides. This often silences genes.
  • Specific Transcription Factors: Proteins that bind to specific DNA sequences, promoting or inhibiting transcription.
  • Alternative RNA Splicing: Different mRNA molecules can be generated from a single gene due to alternative splicing of exons.
  • mRNA Degradation: The lifespan of mRNA impacts the level of protein expression.
  • Protein Degradation: The breakdown of proteins through ubiquitin-proteasome pathway controls protein abundance.

Histone Modifications

  • Chemical modifications (acetylation or methylation) of histone proteins alter chromatin structure and therefore affect gene expression.

DNA Methylation Details

  • The covalent addition of methyl groups to DNA usually involves cytosine bases in CpG dinucleotides.
  • Methylation commonly silences genes or represses gene expression.

Target Gene Expression

  • Transcription Factors (TF) bind to the promoter region of the target gene, leading to gene expression.

Target Gene Silencing

  • Methylated CpG regions in the target gene promoter area can prevent the binding of TFs, preventing gene expression.

3. Gene Transcription Control Elements

  • Sections of non-coding DNA bound by transcription factors.
  • Proximal control elements are close to the promoter region. Distal control elements are farther away and can be called enhancers or silencers.
  • Binding of transcription factors to these elements can enhance or repress gene expression.

4. Alternative RNA Splicing

  • Different mRNA molecules (and thus different proteins) can be generated from the same gene.
  • This occurs through the excision of introns and the different combinations of exons that are joined together.

5. RNA Interference (RNAi)

  • miRNA and siRNA are small, single-stranded RNA molecules that can bind to mRNA.
  • Binding can lead to mRNA degradation or inhibition of translation.

6. Protein Degradation

  • Ubiquitination marks proteins for degradation by the proteasome.

Differential Gene Expression

  • Different genes are active in different cell types in multicellular organisms
  • The presence of different sets of activators, leads to differential expression of genes in liver, lens cells, and other tissues.

Developmental Processes

  • Cytoplasmic Determinants: Unequal distribution of cytoplasmic substances (RNA and proteins) in the egg can influence subsequent cell fates during development
  • Cell Communication (Induction): One cell group can influence the development of another group of cells by contact with cell surface molecules, or the binding of the growth factors.
  • Determination: Subtle molecular changes in a cell commits it to a specific fate, paving the way for the differentiation of tissues in multicellular organisms.
  • Pattern Formation: Cytoplasmic determinants and inductive signals are involved in laying out the body plan of an organism during development
  • Homeotic Genes: These genes govern the anatomical structures of organisms and mutations in them cause structural abnormalities.

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Gene Expression Lecture 5 PDF

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Test your knowledge on key concepts in molecular biology including transcription initiation, gene regulation, and embryonic development. This quiz covers components like micro RNA, bicoid protein, and homeotic genes, essential for understanding developmental biology.

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