أسئلة المحاضرة الثامنة جينتكس (قبل التعديل)
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What is the primary purpose of gene regulation?

  • To stabilize DNA structure
  • To increase the production of all proteins
  • To control the production of specific gene products (correct)
  • To eliminate unnecessary RNA molecules

    • What mechanism involves increasing the number of gene copies to boost protein production?

  • Gene amplification (correct)
  • Transcriptional regulation
  • Gene rearrangement
  • Gene diminution

    • Which statement describes gene diminution?

  • Rearrangement of gene sequences for antibody generation
  • Adding additional genes to enhance function
  • Removal of genes during development (correct)
  • Activation of dormant genes in response to stress

    • How do malignant cells develop resistance to methotrexate?

    <p>By gene amplification of di-hydrofolate reductase</p> Signup and view all the answers

    Which process is crucial in generating antibodies in B-Cells?

    <p>Gene rearrangement</p> Signup and view all the answers

    What is the main clinical consideration mentioned regarding methotrexate?

    <p>Resistance may develop through gene amplification</p> Signup and view all the answers

    What type of gene regulation involves control at the DNA level?

    <p>Alteration of gene content</p> Signup and view all the answers

    Which of the following is NOT a level of eukaryotic gene regulation?

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

    What is the primary effect of adding a methyl group to the C5 of a cytosine base in GC rich regions?

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

    How does the acetylation of lysine residues in histone proteins affect gene expression?

    <p>Facilitates RNA polymerase binding</p> Signup and view all the answers

    What is the role of silencers in gene expression regulation?

    <p>To decrease the rate of gene expression</p> Signup and view all the answers

    What is the consequence of histone deacetylation?

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

    How does the length of the poly A tail affect mRNA stability?

    <p>Longer tails stabilize mRNA and prolong its half-life</p> Signup and view all the answers

    Which process leads to the creation of different peptides from the same gene?

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

    What is the direct effect of demethylation on transcription?

    <p>Converts heterochromatin to euchromatin</p> Signup and view all the answers

    Which of the following statements about methylation and acetylation is true?

    <p>Methylation leads to transcription repression, whereas acetylation promotes activation</p> Signup and view all the answers

    What is the result of gene amplification in malignant cells in relation to methotrexate?

    <p>Increased number of di-hydrofolate reductase genes</p> Signup and view all the answers

    Which process involves the removal of genes from the genome?

    <p>Gene diminution</p> Signup and view all the answers

    During which process do B-Cells generate antibodies?

    <p>Gene rearrangement</p> Signup and view all the answers

    What role does methotrexate serve in the context of cancer treatment?

    <p>It inhibits di-hydrofolate reductase</p> Signup and view all the answers

    What is a consequence of the total loss of genes in red blood cells during their maturation?

    <p>Formation of mature red blood cells without nuclei</p> Signup and view all the answers

    Which statement best describes transcriptional regulation?

    <p>Control over the amount of RNA produced from a gene</p> Signup and view all the answers

    What is the primary focus of post-transcriptional regulation?

    <p>Altering mRNA processing and stability</p> Signup and view all the answers

    Which of the following describes a mechanism by which eukaryotic gene expression can be regulated at the DNA level?

    <p>Modification of histone proteins</p> Signup and view all the answers

    What is the primary effect of acetylation of lysine residues in histone proteins?

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

    What characterizes the silencer regions in DNA regulatory sequences?

    <p>They decrease the rate of gene expression</p> Signup and view all the answers

    Which statement best describes the process of demethylation?

    <p>It reactivates transcription by removing methyl groups</p> Signup and view all the answers

    What is the impact of a longer poly A tail on mRNA?

    <p>It extends the half-life of mRNA</p> Signup and view all the answers

    How does chromatin remodeling primarily affect transcription rates?

    <p>By converting active euchromatin into inactive heterochromatin</p> Signup and view all the answers

    What is the role of DNA methylase in chromatin remodeling?

    <p>To add a methyl group to cytosine bases</p> Signup and view all the answers

    What does alternative splicing accomplish in gene expression?

    <p>It produces different mRNAs leading to diverse peptides</p> Signup and view all the answers

    What occurs when histone deacetylation happens?

    <p>Histones gain positive charges, increasing DNA affinity</p> Signup and view all the answers

    How does gene amplification contribute to drug resistance in cancer therapies?

    <p>Gene amplification increases the number of genes for di-hydrofolate reductase, which allows malignant cells to overcome the effects of methotrexate.</p> Signup and view all the answers

    What is the significance of gene rearrangement in B-Cells?

    <p>Gene rearrangement is crucial for the generation of diverse antibodies in B-Cells.</p> Signup and view all the answers

    What happens to gene content during the maturation of red blood cells?

    <p>Red blood cells undergo gene diminution, resulting in the complete loss of their gene content.</p> Signup and view all the answers

    In what ways can post-transcriptional regulation influence gene expression?

    <p>Post-transcriptional regulation can alter mRNA stability, translation efficiency, and RNA splicing.</p> Signup and view all the answers

    Explain the role of transcriptional regulation in gene expression.

    <p>Transcriptional regulation controls the synthesis of RNA from DNA, determining the amount of gene product produced.</p> Signup and view all the answers

    What are the clinical implications of gene amplification in cancer treatment?

    <p>Clinically, gene amplification can lead to resistance against drugs like methotrexate, making treatment less effective.</p> Signup and view all the answers

    What is meant by gene diminution and where does it occur?

    <p>Gene diminution refers to the removal of genes from the genome, such as in the development of red blood cells.</p> Signup and view all the answers

    Describe how gene amplification can impact antibiotic resistance mechanisms.

    <p>Gene amplification can increase the expression of resistance genes, leading to higher levels of antibiotic resistance.</p> Signup and view all the answers

    How does DNA methylation influence the transition from euchromatin to heterochromatin?

    <p>DNA methylation promotes the conversion of active euchromatin into inactive heterochromatin, thereby reducing the rate of transcription.</p> Signup and view all the answers

    What is the effect of histone acetylation on RNA polymerase binding?

    <p>Histone acetylation decreases the positive charges on histones, reducing their affinity for DNA and facilitating RNA polymerase binding.</p> Signup and view all the answers

    How do enhancers and silencers differ in their function related to gene expression?

    <p>Enhancers increase the rate of gene expression, while silencers decrease it.</p> Signup and view all the answers

    What role does alternative splicing play in protein diversity?

    <p>Alternative splicing allows a single gene to produce different peptides with varied functions.</p> Signup and view all the answers

    In what way does the poly A tail influence the half-life of mRNA?

    <p>A longer poly A tail extends the half-life of mRNA by stabilizing it against degradation by exonucleases.</p> Signup and view all the answers

    What effect does the deacetylation of histones have on transcription activity?

    <p>Deacetylation of histones reverses the acetylation process, leading to inactivation of transcription.</p> Signup and view all the answers

    Why is the methylation of cytosine in GC rich regions significant for gene regulation?

    <p>Methylation of cytosine in GC rich regions is significant because it regulates gene expression by leading to chromatin condensation and silencing.</p> Signup and view all the answers

    Describe how demethylation affects gene transcription.

    <p>Demethylation can reactivate transcription by converting inactive heterochromatin back to active euchromatin.</p> Signup and view all the answers

    What role does gene rearrangement play in the immune system?

    <p>Gene rearrangement is crucial for generating a diverse range of antibodies produced by B-Cells.</p> Signup and view all the answers

    How does gene amplification contribute to the resistance of malignant cells to methotrexate?

    <p>Malignant cells increase the number of genes for di-hydrofolate reductase, making them less sensitive to methotrexate.</p> Signup and view all the answers

    Describe gene diminution and provide an example of where it occurs.

    <p>Gene diminution refers to the removal of genes from the genome, such as the loss of all genes in red blood cells during maturation.</p> Signup and view all the answers

    What is the significance of transcriptional regulation in gene expression?

    <p>Transcriptional regulation controls the level of mRNA production, thereby influencing the amount of specific proteins synthesized.</p> Signup and view all the answers

    What impact does post-transcriptional regulation have on gene expression?

    <p>Post-transcriptional regulation can modify RNA after transcription, affecting its stability, splicing, and translation.</p> Signup and view all the answers

    How do enhancers function in the regulation of gene expression?

    <p>Enhancers are DNA sequences that promote transcription by enabling the binding of transcription factors to increase gene expression.</p> Signup and view all the answers

    Explain the relationship between DNA methylation and gene expression.

    <p>DNA methylation often represses gene expression by inhibiting the binding of transcription factors to the gene.</p> Signup and view all the answers

    What effect does acetylation of histones have on gene expression?

    <p>Acetylation of histones reduces the positive charge on histones, leading to a more relaxed chromatin structure and increased gene expression.</p> Signup and view all the answers

    What is the consequence of methylation of cytosine bases in gene transcription?

    <p>Methylation leads to a decrease in the transcription rate by converting active euchromatin into inactive heterochromatin.</p> Signup and view all the answers

    How does histone acetylation promote gene expression?

    <p>Histone acetylation reduces the positive charges on lysine residues, decreasing affinity between histones and DNA, thereby facilitating the binding of transcription machinery.</p> Signup and view all the answers

    What are enhancers and their role in gene expression?

    <p>Enhancers are DNA sequences that increase the rate of gene expression by facilitating the binding of transcription factors.</p> Signup and view all the answers

    What is the effect of deacetylation of histones on transcription?

    <p>Deacetylation of histones leads to enhanced positive charges, increasing the affinity between histones and DNA, which represses transcription.</p> Signup and view all the answers

    Explain the significance of alternative splicing in gene expression.

    <p>Alternative splicing allows for the production of multiple protein isoforms from a single gene, increasing protein diversity and functionality.</p> Signup and view all the answers

    How does the length of the poly A tail influence mRNA stability?

    <p>A longer poly A tail stabilizes mRNA by protecting its 3' end from degradation by exonucleases, leading to a longer half-life.</p> Signup and view all the answers

    In what way does demethylation affect transcription?

    <p>Demethylation reactivates transcription by converting heterochromatin back to euchromatin, thus restoring access for transcription factors.</p> Signup and view all the answers

    What distinguishes silencers from enhancers in gene regulation?

    <p>Silencers are DNA sequences that decrease the rate of gene expression, acting as repressors, while enhancers increase gene expression.</p> Signup and view all the answers

    Study Notes

    Regulation of Gene Expression

    • Central Dogma of Molecular Biology: Mechanisms that increase or decrease production of specific gene products (protein or RNA).
    • Levels of Eukaryotic Gene Regulation:
      • Alteration of gene content (DNA level)
      • Transcriptional regulation (transcription level)
      • Post-transcriptional regulation

    Gene Amplification

    • Increases the number of gene copies, leading to increased protein production
    • Example: Malignant cells develop resistance to methotrexate by increasing the number of di-hydrofolate reductase genes, the target for methotrexate

    Gene Diminution

    • Removal of one or more genes from the genome
    • Example: Red blood cells lose all genes during development after sufficient Hemoglobin RNA is synthesized

    Gene Rearrangement (Recombination)

    • Plays a major role in antibody (immunoglobulin) production by B-Cells

    Methotrexate Clinical Application

    • Methotrexate, an anti-cancer drug, inhibits di-hydrofolate reductase
    • Long-term therapy can lead to drug resistance in cancer cells due to gene amplification of di-hydrofolate reductase

    DNA Cytosine Methylation

    • Addition of a methyl group to the C5 of cytosine base in GC-rich regions by DNA methyltransferase
    • Decreases transcription rate by converting active euchromatin into inactive heterochromatin
    • Deamethylation reactivates transcription

    Histone Acetylation

    • Acetylation of lysine residues in histone proteins removes positive charges, decreasing affinity between histone and DNA
    • This allows RNA polymerase and transcription factors to bind to the promoter region, activating transcription
    • Deacetylation by deacetylase enzymes reverses this process, inactivating transcription

    DNA Regulatory Regions

    • Specific DNA sequences present upstream of the transcription start initiation point

    Enhancers

    • Increase the rate of gene expression

    Silencers (Repressers)

    • Decrease the rate of gene expression

    Alternative Splicing

    • Produces different peptides with different functions by alternative RNA processing

    RNA Stability

    • mRNA half-life is variable, ranging from minutes to days
    • A longer poly A tail stabilizes mRNA, protecting the 3’ end from degradation by exonuclease enzymes, extending mRNA half-life

    Regulation of Gene Expression

    • Gene expression regulation involves mechanisms that increase or decrease the production of specific gene products, which are proteins or RNA.
    • Eukaryotic gene regulation occurs at different levels: alteration of gene content (DNA level), transcriptional regulation (transcription level), and post-transcriptional regulation.

    Alteration of Gene Content

    • Gene Amplification: This involves increasing the number of gene copies, leading to increased protein production. For example, malignant cells can develop resistance to methotrexate by amplifying genes for di-hydrofolate reductase, which is the target for methotrexate.
    • Gene Diminution: This involves removing a gene or genes from the genome. For example, red blood cells completely lose all their genes during development, discarding their nuclei after sufficient hemoglobin RNA is synthesized.
    • Gene Rearrangement (Recombination): This process plays a significant role in the generation of antibodies (immunoglobulins) produced by B-cells.

    Transcriptional Regulation

    • DNA Cytosine Methylation: This involves adding a methyl group to the C5 of cytosine base in GC-rich regions, catalyzed by DNA methylase. This methylation decreases the rate of transcription by converting active euchromatin into inactive heterochromatin. Deamethylation is required to reactivate transcription.
    • Histone Acetylation: This process involves the acetylation of lysine residues of histone proteins, removing positive charges and decreasing the affinity between histones and DNA. This facilitates the binding of RNA polymerase and transcription factors to the promoter region, activating transcription. Deacetylase enzymes reverse the process, inactivating transcription.

    DNA Regulatory Regions

    • Enhancers: These are specific DNA sequences located upstream from the transcription start initiation point. They increase the rate of gene expression.
    • Silencers (Repressors): These are specific DNA sequences also located upstream from the transcription start initiation point, but they decrease the rate of gene expression.

    Post-Transcriptional Regulation

    • Alternative Splicing: This process produces different peptides with distinct functions from a single mRNA molecule.
    • RNA Stability: The half-life of mRNA is variable, ranging from a few minutes to days. A longer poly A tail stabilizes mRNA by protecting its 3' end from degradation by exonuclease enzymes, leading to a longer half-life.

    Regulation of Gene Expression

    • Gene expression refers to mechanisms that increase or decrease the production of specific gene products, such as proteins or RNA.
    • Eukaryotic gene regulation can occur at different levels:
      • Alteration of gene content: Involves changes in the number of gene copies within the genome.
      • Transcriptional regulation: Controls the rate of transcription, the process of copying DNA into RNA.
      • Post-transcriptional regulation: Includes various mechanisms that occur after transcription, such as RNA processing and stability.

    Gene Amplification

    • Increase in gene copies leads to increased protein production.
    • Example: Cancer cells can develop resistance to methotrexate, a chemotherapy drug, by increasing the number of genes for dihydrofolate reductase, the target of methotrexate.

    Gene Diminution

    • Gene diminution involves the removal of genes from the genome.
    • Example: Mature red blood cells lose their nuclei during development, discarding genes as they synthesize hemoglobin mRNA.

    Gene Rearrangement (Recombination)

    • Gene rearrangement plays a crucial role in the production of antibodies (immunoglobulins) by B-cells.

    Clinical Application of Gene Amplification

    • Methotrexate is used as an anticancer drug and inhibits dihydrofolate reductase.
    • Long term methotrexate therapy can lead to cancer cell resistance due to gene amplification increasing the number of dihydrofolate reductase genes.

    Chromatin Remodeling

    • DNA Cytosine Methylation*
    • Involves the addition of a methyl group to the cytosine base in GC-rich regions by DNA methylase.
    • Methylation reduces the rate of transcription, converting active euchromatin into inactive heterochromatin.
    • Deamethylation reactivates transcription.
    • Histone Acetylation*
    • Acetylation of lysine residues in histone proteins removes positive charges, reducing the affinity between histones and DNA.
    • This makes it easier for RNA polymerase and transcription factors to bind to the promoter region, activating transcription.
    • Deacetylation by deacetylase enzymes reverses the process, inhibiting transcription.

    DNA Regulatory Regions

    • Specific DNA sequences located upstream of the transcription start site play a role in gene regulation.
    • Enhancers increase the rate of gene expression.
    • Silencers (Repressers) decrease the rate of gene expression.

    Alternative Splicing

    • Alternative RNA processing leads to the production of different protein isoforms with varying functions.

    RNA Stability

    • Messenger RNA (mRNA) half-life varies, ranging from minutes to days.
    • A longer poly-A tail stabilizes mRNA, protecting it from degradation and extending its half-life.

    Central Dogma of Molecular Biology

    • Gene regulation is the mechanism by which a cell controls the production of specific gene products (proteins or RNA).
    • Gene regulation occurs at different levels:
      • Alteration of gene content (control at DNA level)
      • Transcriptional regulation (control at transcription level)
      • Post-transcriptional regulation

    Gene Amplification

    • Increasing the number of gene copies leads to increased protein production.
    • Example: Malignant cells develop resistance to methotrexate by increasing the number of genes for di-hydrofolate reductase, the target for methotrexate.

    Gene Diminution

    • Removal of a gene or genes from the genome.
    • Example: Complete loss of all genes in red blood cells during development – red blood cells discard their nuclei once sufficient hemoglobin RNA is synthesized.

    Gene Rearrangement

    • Plays a major role in the generation of antibodies (immunoglobulins) produced by B-cells.

    Clinical Application

    • Methotrexate is an anticancer drug that inhibits di-hydrofolate reductase.
    • Long-term therapy with methotrexate can result in cancer cells developing resistance to the drug by increasing the number of genes for di-hydrofolate reductase through gene amplification.

    DNA Cytosine Methylation

    • Methylation is the addition of a methyl group to the C5 of cytosine base in GC-rich regions by the DNA methylase enzyme.
    • DNA methylation decreases the rate of transcription as it converts the active euchromatin into inactive heterochromatin.
    • Reactivation occurs through demethylation.

    Histone Acetylation

    • Acetylation of lysine residues of histone proteins removes their positive charges.
    • This decreases the affinity between histone and DNA, allowing RNA polymerase and transcription factors to bind to the promoter region more easily, activating transcription.
    • Deacetylation of histone proteins by deacetylase enzymes reverses this process, leading to inactivation of transcription.

    DNA Regulatory Regions

    • These are specific DNA sequences located upstream from the transcription start initiation point. They include:
      • Enhancers: Increase rate of gene expression.
      • Silencers (Repressers): Decrease rate of gene expression.

    Alternative Splicing

    • Alternative RNA processing leads to the production of different peptides with different functions.

    RNA Stability

    • The half-life of mRNA varies significantly, lasting from a few minutes to days.
    • The longer the poly A tail, the longer the half-life of mRNA. This is because the poly A tail stabilizes mRNA by protecting its 3’ end from attack by exonuclease enzymes.

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