Epigenome Editing and Engineering Quiz
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Questions and Answers

What is the primary difference between epigenetic editing and gene editing?

  • The type of engineered molecules used
  • The persistence of alterations across cell divisions
  • The specific sites targeted in the genome
  • The modification of the DNA sequence itself (correct)

    • What is the effect of epigenetic alterations on gene expression?

  • They have no effect on gene expression
  • They are always temporary and reversible
  • They alter the presentation of DNA sequences to proteins (correct)
  • They alter the DNA sequence itself

    • What is the mechanism by which epigenetic changes are transmitted through mitosis?

  • Histone protein modification
  • DNA methylation
  • Changes in DNA binding factors
  • Alterations in chromatin structure (correct)

    • What is the primary factor that influences epigenetic alterations?

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

    What is the definition of epigenetics?

    <p>The alteration of gene expression without DNA sequence change</p> Signup and view all the answers

    What is the purpose of DNA methylation in epigenetic change?

    <p>To add methyl groups to nucleotide bases</p> Signup and view all the answers

    What is the configuration of methylated cytosine bases in CpG dinucleotides?

    <p>Two methylated cytosine bases sit diagonally across from each other on opposite strands</p> Signup and view all the answers

    What is the state of the cytosine base on the newly replicated strand immediately after semiconservative replication?

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

    How do methyl groups in the major groove of DNA affect transcription?

    <p>They inhibit the binding of transcription factors</p> Signup and view all the answers

    What is the result of DNA methylation attracting histone deacetylase enzymes?

    <p>Chromatin structure is altered to repress transcription</p> Signup and view all the answers

    What is the term for the modification of histone proteins?

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

    What is the primary function of histone modifications in chromatin structure?

    <p>To alter chromatin structure and affect transcription</p> Signup and view all the answers

    What is the net result of DNA methylation on gene expression?

    <p>It represses gene expression</p> Signup and view all the answers

    What is the effect of histone acetylation on chromatin structure?

    <p>It destabilizes chromatin structure, increasing transcription</p> Signup and view all the answers

    Which type of histone modification is associated with both increased and decreased transcription?

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

    What is the predominant type of DNA methylation in eukaryotes?

    <p>Methylation of cytosine to produce 5-methylcytosine</p> Signup and view all the answers

    What is the term used to describe histone modifications that affect chromatin structure and transcription?

    <p>Epigenetic marks</p> Signup and view all the answers

    How many unique potential changes in histones can occur due to modifications at different amino acids?

    <p>100</p> Signup and view all the answers

    What is the term for the regions of DNA that have many CpG dinucleotides?

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

    What is the effect of methylation of CpG islands near a gene?

    <p>Repression of gene transcription</p> Signup and view all the answers

    What is the role of histone modifications in transcription?

    <p>They serve as binding sites for transcription factors</p> Signup and view all the answers

    What is the role of demethylases in gene expression?

    <p>Removing methyl groups from cytosine bases</p> Signup and view all the answers

    Why is it important for epigenetic changes to be maintained during cell division?

    <p>To enable the inheritance of epigenetic phenotypes</p> Signup and view all the answers

    What is the process by which cells repress and activate genes through DNA methylation?

    <p>Methylation and demethylation</p> Signup and view all the answers

    What is the likely effect of adding three methyl groups to lysine 4 in the H3 histone?

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

    What is the role of the polycomb group (PcG) proteins in histone modification?

    <p>Repressing transcription by modifying histones</p> Signup and view all the answers

    What is the consequence of ubiquitination of histone H2B?

    <p>Repair of double-strand breaks in DNA</p> Signup and view all the answers

    What is the role of histone modifications in the cell cycle?

    <p>Influencing other molecular processes such as cell cycle checkpoint signalling</p> Signup and view all the answers

    What is the link between epigenetic effects and cancer?

    <p>Encouraging evidence has linked epigenetic effects to oncogenesis</p> Signup and view all the answers

    What is the definition of epigenetics?

    <p>The study of heritable changes in gene expression that are not encoded in the DNA of the genome</p> Signup and view all the answers

    Study Notes

    Epigenome Editing and Epigenetics

    • Epigenetic editing is a type of genetic engineering that modifies the epigenome at specific sites using engineered molecules targeted to those sites.
    • Epigenetic editing involves modifying and presenting DNA sequences to proteins and other DNA binding factors that influence DNA function.
    • Epigenetics alters the expression of genes without alterations in the DNA sequence, and these alterations are stable enough to be transmitted through mitosis and sometimes meiosis.
    • Epigenetic changes can also be influenced by environmental factors.

    DNA Methylation

    • DNA methylation is the addition of methyl groups to nucleotide bases, specifically cytosine, to produce 5-methylcytosine.
    • Methylation often occurs on cytosine nucleotides immediately adjacent to guanine nucleotides, referred to as CpG dinucleotides.
    • CpG islands are regions with many CpG dinucleotides and are often located in or near gene promoters.
    • Methylation of CpG islands near a gene leads to repression of transcription.

    Maintenance of Methylation

    • Methylation of CpG dinucleotides means that two methylated cytosine bases sit diagonally across from each other on opposite strands.
    • Before replication, cytosine bases on both strands are methylated, and immediately after replication, the cytosine base on the template strand is methylated, but the cytosine base on the newly replicated strand is unmethylated.
    • Special methyl-transferase enzymes recognize the hemi-methylated state of CpG dinucleotides and add methyl groups to the unmethylated cytosine bases, resulting in two new DNA molecules that are fully methylated.

    Repression of Transcription by DNA Methylation

    • The methyl group of 5-methylcytosine sits within the major groove of the DNA molecule, inhibiting the binding of transcription factors and other proteins required for transcription.
    • The presence of the methyl group in the major groove attracts certain proteins that directly repress transcription.
    • DNA methylation also attracts histone deacetylase enzymes, which remove acetyl groups from the tails of histone proteins, altering chromatin structure in a way that represses transcription.

    Histone Modifications

    • Histone modifications can also occur through the addition of phosphates, methyl groups, acetyl groups, and ubiquitin.
    • These modifications can occur at different amino acids on different histones and create more than 100 unique potential changes in the histones.
    • Many of these modifications alter chromatin structure and affect transcription of genes.

    Specific Histone Modifications

    • Histone acetylation: addition of acetyl groups to amino acids in the histone tails, generally destabilizing chromatin structure and increasing transcription.
    • Histone methylation: addition of methyl groups to histones, altering chromatin structure and affecting transcription, with different effects depending on the specific amino acid methylated.
    • Histone ubiquitination: modification of histones, influencing other molecular processes such as DNA repair and cell cycle checkpoint signaling.

    Importance of Epigenome Editing

    • Epigenetic effects have been linked to oncogenesis, progression, and treatment of cancer.
    • Epigenetics plays a role in many cellular processes, making epigenome editing a crucial area of research.

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    Description

    Test your knowledge on epigenome editing, a type of genetic engineering that modifies the epigenome at specific sites using engineered molecules. Learn about the differences between epigenetic editing and gene editing, and how it affects DNA function.

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