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

What is a primary function of epigenetic changes?

<p>They allow for reversible modifications to gene activity. (A)</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 (D)</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. (C)</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) (C)</p> Signup and view all the answers

Which of the following is a major epigenetic regulator?

<p>Histone modifications (A)</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 (A)</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 (D)</p> Signup and view all the answers

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

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

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

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

What is the primary chemical change involved in DNA methylation?

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

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

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

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

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

How does DNA methylation typically affect gene expression?

<p>It blocks gene transcription (D)</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 (C)</p> Signup and view all the answers

What effect does histone methylation have on DNA?

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

How does acetylation impact eukaryotic proteins?

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

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

<p>RISC (D)</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. (B)</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 (C)</p> Signup and view all the answers

What is generally associated with a global loss of methylation?

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

What could influence DNA methylation patterns according to epigenetic studies?

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

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

<p>Next-generation sequencing (A)</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 (D)</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 (D)</p> Signup and view all the answers

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

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

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

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

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

<p>Leads to genomic instability (C)</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 (B)</p> Signup and view all the answers

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

<p>Nonmonotonic changes (C)</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 (B)</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. (C)</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 (D)</p> Signup and view all the answers

Flashcards

Epigenetics

Regulates gene expression by modifying protein expression levels without changing the DNA sequence.

Histone modification

An epigenetic regulator that alters histone proteins to affect gene expression.

DNA methylation

Adding a methyl group to cytosine bases, often silencing genes.

Noncoding RNA expression

A mechanism controlling gene expression through non-protein-coding RNAs.

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Post-translational modification

Changes to proteins after their synthesis.

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Methylation (protein)

Adding a methyl group to a protein.

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Acetylation

Adding an acetyl group to a protein.

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Phosphorylation

Adding a phosphate group to a protein.

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Glycosylation

Adding a sugar molecule to a protein.

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CpG dinucleotides

Cytosine followed by guanine in DNA. Often sites of DNA methylation.

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Chromatin remodeling

Changes in chromatin structure affecting DNA accessibility.

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MicroRNAs (miRNAs)

Small non-coding RNAs that regulate gene expression.

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RISC complex

RNA-induced silencing complex, miRNA's partner in gene regulation.

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DNA methyltransferase (DNMT)

Enzyme that adds methyl groups to DNA.

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S-adenosylmethionine (SAM)

Cofactor for DNA methylation.

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Histone methylation

Adding methyl groups to histone proteins.

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CpG islands

DNA regions rich in CpG dinucleotides.

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5-mC

Methylated cytosine.

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Gene expression

Process by which a gene's information is used to make a functional product.

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Proteome

Complete set of proteins produced by an organism.

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Transcription

Synthesis of an RNA molecule from a DNA template.

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Arsenic

Environmental toxin linked to altered methylation patterns.

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Bisphenol-A (BPA)

Environmental chemical linked to hypomethylation.

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Tobacco smoke

Linked to global hypomethylation and genomic instability.

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Environmental factors

External factors impacting epigenetic modifications.

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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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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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