Epigenetics and Post-Translational Modifications
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Questions and Answers

What role does DNA methylation play in gene expression?

  • It inhibits the binding of transcription factors to promoters. (correct)
  • It facilitates chromatin remodeling.
  • It promotes the binding of transcription factors to promoters.
  • It enhances DNA replication.

    • Which of the following is NOT an epigenetic mechanism that influences gene expression?

  • DNA methylation
  • Chromatin remodeling
  • Histone acetylation
  • mRNA splicing (correct)

    • How do microRNAs influence gene expression?

  • By enhancing the translation of proteins.
  • By promoting transcription of target genes.
  • By altering DNA sequences directly.
  • By degrading mRNA molecules. (correct)

    • What effect does chromatin remodeling have on gene expression?

    <p>It alters the accessibility of DNA for transcription.</p> Signup and view all the answers

    What is a primary function of epigenetic changes?

    <p>They allow for reversible modifications to gene activity.</p> Signup and view all the answers

    Which of the following processes does NOT represent a way to modify protein expression after translation?

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

    What role do post-translational modifications (PTMs) play in cellular function?

    <p>They regulate protein activity and interaction.</p> Signup and view all the answers

    What is the primary mechanism through which the epigenome influences gene expression?

    <p>Modification of messenger RNA (mRNA)</p> Signup and view all the answers

    Which of the following is a major epigenetic regulator?

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

    How many genes are estimated to be present in the human genome?

    <p>Around 21,000 - 22,000</p> Signup and view all the answers

    Single genes in the human genome can encode multiple proteins through which of the following mechanisms?

    <p>Genomic recombination</p> Signup and view all the answers

    What is the significance of cytosine phosphate-guanine (CpG) DNA methylation?

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

    Which of the following is NOT a function of post-translational modifications?

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

    What is the primary chemical change involved in DNA methylation?

    <p>Addition of a methyl group</p> Signup and view all the answers

    What region of the genome is typically associated with high levels of DNA methylation?

    <p>CpG islands</p> Signup and view all the answers

    Which enzyme is primarily responsible for adding methyl groups to cytosine bases?

    <p>DNA methyltransferase (DNMT)</p> Signup and view all the answers

    What role does S-adenosylmethionine (SAM) play in DNA methylation?

    <p>It acts as a substrate for methyltransferases</p> Signup and view all the answers

    How does DNA methylation typically affect gene expression?

    <p>It blocks gene transcription</p> Signup and view all the answers

    What is the function of maintenance methyltransferase after DNA replication?

    <p>To methylate cytosines on the daughter strand</p> Signup and view all the answers

    What effect does histone methylation have on DNA?

    <p>It restricts access to transcription factors</p> Signup and view all the answers

    How does acetylation impact eukaryotic proteins?

    <p>It transfers an acetyl group to nitrogen</p> Signup and view all the answers

    What complex do mature miRNAs form with proteins to regulate gene expression?

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

    How does extensive complementarity between miRNA and target mRNA affect the target mRNA?

    <p>It is rapidly degraded.</p> Signup and view all the answers

    What role does DNA methylation play in gene expression?

    <p>Regulates gene expression without altering the DNA sequence</p> Signup and view all the answers

    What is generally associated with a global loss of methylation?

    <p>Genomic instability and aging</p> Signup and view all the answers

    What could influence DNA methylation patterns according to epigenetic studies?

    <p>Environmental exposures and nutritional status</p> Signup and view all the answers

    What technology is NOT commonly used to assess global measures of methylation?

    <p>Next-generation sequencing</p> Signup and view all the answers

    Which developmental conditions have been associated with gains in global methylation levels?

    <p>Gestational diabetes and Down syndrome</p> Signup and view all the answers

    What is the primary function of the enzyme DNMT in relation to DNA methylation?

    <p>Adds methyl groups to DNA</p> Signup and view all the answers

    Which of the following health outcomes are associated with arsenic exposure?

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

    How does BPA exposure affect DNA methylation in women and young girls?

    <p>Induces hypomethylation</p> Signup and view all the answers

    What is a potential impact of tobacco smoke exposure on the epigenome?

    <p>Leads to genomic instability</p> Signup and view all the answers

    Which genes are affected by BPA exposure, particularly in relation to methylation?

    <p>SNORD complex, SULT2A1, and COMT</p> Signup and view all the answers

    Which type of changes in DNA methylation does fetal exposure to BPA induce?

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

    What is the effect of tobacco smoke on DNA methylation patterns over time?

    <p>Patterns remain stable over time</p> Signup and view all the answers

    Which statement is true regarding sex differences in arsenic's effect on DNA methylation?

    <p>The effects of arsenic vary by sex.</p> Signup and view all the answers

    What kind of methylation alterations are commonly observed with arsenic exposure?

    <p>Mixed effects including both hypomethylation and hypermethylation</p> Signup and view all the answers

    Study Notes

    Epigenetics Overview

    • Epigenetics regulates gene expression by modifying protein expression levels without altering the DNA sequence.
    • Epigenetic modifications allow organisms to rapidly adapt to environmental changes.
    • The three main epigenetic regulators are:
      • Histone modifications
      • DNA methylation
      • Noncoding RNA expression

    Post-Translational Modifications

    • Post-translational modifications alter proteins after translation.
    • These modifications include:
      • Methylation
      • Acetylation
      • Phosphorylation
      • Glycosylation
    • These modifications influence protein folding, stability, location in the cell, function, activation, and interactions with other molecules.
    • Post-translational modifications significantly increase the diversity of the proteome, which is the complete set of proteins produced by an organism.

    Epigenetic Mechanisms

    • DNA methylation involves adding a methyl group (CH3) to cytosine bases in CpG dinucleotides.
      • This modification usually inhibits transcription factors from binding to promoters.
      • DNA methylation patterns are passed on to daughter cells during DNA replication.
    • Chromatin remodeling (including histone methylation and acetylation) affects the structure of chromatin.
      • This structure influences the accessibility of DNA for transcription.
    • MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression post-transcriptionally.
      • They regulate gene expression by targeting specific messenger RNAs (mRNAs).

    DNA Methylation

    • DNA Methylation is the addition of a methyl group to the fifth carbon position of a cytosine base.
    • Methylated cytosine (5-mC) bases are often located near guanine-5 CpG methylation.
    • CpG methylation occurs in regions of the genome with high cytosine-guanine (CG) content. These regions are called CpG islands.
    • The DNA methyltransferase (DNMT) enzyme family adds methyl groups to cytosine bases.
    • The process requires the cofactor S-adenosylmethionine (SAM).

    Chromatin Remodeling: Histone Methylation

    • Histone methylation influences the accessibility of DNA for transcription.
    • Histone methylation can involve adding one or multiple methyl groups to amino acid residues.

    Acetylation

    • Acetylation is the transfer of an acetyl group to nitrogen.
    • It occurs in almost all eukaryotic proteins through both irreversible and reversible mechanisms.

    MicroRNAs

    • Mature miRNAs assemble with proteins to form a complex called RISC.
    • RISC searches for mRNAs with complementary nucleotide sequences to the bound miRNA.
    • Depending on the extent of the complementarity, the target mRNA is either degraded or transferred to an area of the cytoplasm where it is destroyed.
    • miRNAs are important epigenetic regulators of gene and protein expression.
    • They play a role in developmental processes and are influenced by environmental chemicals.

    Epigenetics and the Environment

    • Environmental factors can influence epigenetic modifications.
    • Large-scale changes in methylation processes, due to environmental exposure, nutritional status, or disease, can cause global losses or gains of methylation.
    • Global loss of methylation is associated with genomic instability, aging, and cancer.
    • Global gains in methylation, particularly in the placenta, have been associated with developmental defects, including Down syndrome and gestational diabetes.

    Current Research

    • Arsenic Exposure:
      • Arsenic exposure is linked to altered methylation patterns in adults and infants, resulting in hypomethylation and hypermethylation.
      • Arsenic's effects on DNA methylation may vary by sex.
      • Arsenic exposure is associated with gene-specific methylation changes, often resulting in hypermethylation.
    • Bisphenol-A (BPA) Exposure:
      • BPA induces hypomethylation in women and young girls.
      • Fetal BPA exposure is associated with non-monotonic changes in DNA methylation in the liver.
      • BPA alters methylation patterns in the placenta, fetal liver, and fetal kidney.
    • Tobacco Smoke Exposure:
      • Tobacco smoke exposure is associated with genomic instability and epigenetic dysregulation.
      • Both in utero and adult exposure to tobacco smoke have been linked to global hypomethylation.
      • Tobacco smoke exposure impacts genes related to cancer, cell cycle, metabolism, and fetal growth.

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    Environmental Influences On The Epigenome Lecture 7-8 PDF

    Description

    This quiz covers the fundamentals of epigenetics and post-translational modifications, exploring how these processes regulate gene expression and protein functionality. Participants will learn about key mechanisms such as DNA methylation, histone modifications, and various forms of post-translational modifications. Test your understanding of these essential biological processes.

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