Environmental Influences on the Epigenome
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Questions and Answers

What is the primary role of DNA methylation in gene expression?

  • To promote histone acetylation
  • To enhance transcription factor binding
  • To facilitate mRNA splicing
  • To inhibit transcription factor binding (correct)

Which regions of the genome are typically enriched with CpG methylation?

  • CpG islands (correct)
  • Promoter regions without methylation
  • Intron regions
  • Exons

What enzyme family is responsible for adding methyl groups to cytosine during DNA methylation?

  • DNA methyltransferases (correct)
  • Chromatin remodeling complexes
  • RNA polymerases
  • Histone deacetylases

What is the cofactor required for the process of DNA methylation?

<p>S-adenosylmethionine (SAM) (C)</p> Signup and view all the answers

What type of RNA molecules are involved in post-transcriptional regulation of gene expression?

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

How are DNA methylation patterns inherited during cell division?

<p>By maintenance methyltransferase (C)</p> Signup and view all the answers

What is the effect of histone acetylation on chromatin structure?

<p>Promotes a more accessible chromatin structure (B)</p> Signup and view all the answers

Which statement is NOT true regarding DNA methylation?

<p>It is a transient modification. (D)</p> Signup and view all the answers

What is the outcome of the interaction between maintenance methyltransferase and hybrid double helices?

<p>It methylates CG sequences paired with already methylated strands. (C)</p> Signup and view all the answers

How does histone methylation affect gene transcription?

<p>It promotes access to DNA for transcription. (A)</p> Signup and view all the answers

What is the primary mechanism of N-terminal acetylation in proteins?

<p>It is co-translational and involves replacing methionine. (D)</p> Signup and view all the answers

Which enzymes are responsible for adding acetyl groups to histone proteins?

<p>Histone acetylases (HATs) (D)</p> Signup and view all the answers

What is the biological significance of acetylation in eukaryotic proteins?

<p>Its exact biological significance is still unclear. (B)</p> Signup and view all the answers

What role does histone deacetylation play in gene regulation?

<p>It reduces accessibility, potentially inhibiting transcription. (B)</p> Signup and view all the answers

How can amino acid residues be modified through methylation?

<p>They can be conjugated to either one or multiple methyl groups. (C)</p> Signup and view all the answers

What outcome is most likely from a single lysine alteration on histones?

<p>It may influence cellular homeostasis. (D)</p> Signup and view all the answers

What is often associated with global loss of methylation?

<p>Common phenotype of aging (B)</p> Signup and view all the answers

Which technology is NOT used for assessing global methylation levels?

<p>DNA sequencing (B)</p> Signup and view all the answers

How can individual genetic variations affect a person's epigenome?

<p>By modifying responses to environmental exposures (B)</p> Signup and view all the answers

What developmental defects have been linked to gains in global methylation levels?

<p>Down syndrome and gestational diabetes (B)</p> Signup and view all the answers

Which aspect of methylation patterns does current technology enable researchers to assess?

<p>Site-specific methylation (C)</p> Signup and view all the answers

What was the focus of the study conducted by Heijmans et al. in human populations?

<p>Prenatal exposure to famine on IGF2 methylation (D)</p> Signup and view all the answers

Gene-specific alterations in methylation have been particularly linked to which period?

<p>Prenatal period (A)</p> Signup and view all the answers

The relationship between environmental exposures and DNA methylation is best described as:

<p>Complex and interactive (B)</p> Signup and view all the answers

Flashcards

DNA Methylation

Adding a methyl group to a cytosine base in DNA, typically at a CpG site, often silencing gene expression.

CpG site

A DNA sequence where a cytosine nucleotide is followed by a guanine nucleotide.

Methyltransferase

Enzyme that adds methyl groups to DNA.

5-methylcytosine (5-mC)

Cytosine with a methyl group attached.

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Gene silencing

Turning off gene expression.

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Chromatin Remodeling

Changes in the structure of chromatin, affecting gene expression.

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Epigenetics

Study of heritable changes in gene expression without altering DNA sequence.

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Histone modification

Altering histones, affecting DNA packaging and gene expression.

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Post-translational modifications

Changes to proteins after they are made

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Methylation

Adding a methyl group to a protein

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Phosphorylation

Adding a phosphate group to a protein

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Histone methylation

Adding methyl groups to histones, affecting DNA accessibility

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Histone acetylation

Adding acetyl groups to histones, making DNA more accessible

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N-terminal acetylation

Adding an acetyl group to the nitrogen of the first amino acid (N-terminus).

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Histone acetylases (HATs)

Enzymes that add acetyl groups to histones

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Histone deacetylases (HDACs)

Enzymes removing acetyl groups from histones

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Epigenome's Response to Environment

Individual genetic differences influence how a person's epigenome reacts to environmental exposures, leading to unique responses.

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Global Methylation Changes

Large-scale alterations in methylation patterns due to environmental factors like exposure, nutrition, or disease, can result in overall losses or gains of methylation, especially during early development.

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Global Methylation Loss

A widespread decrease in methylation is often linked to genomic instability and is common in aging and cancer.

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Global Methylation Gain

Increased methylation levels, particularly in the placenta, have been associated with developmental problems such as Down syndrome and gestational diabetes.

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Site-Specific Methylation

Current technology allows researchers to measure methylation at specific DNA locations, providing detailed insights into disease development and susceptibility.

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Gene-Specific Methylation and Health

Changes in methylation at specific genes, especially those occurring before birth, are linked to environmental exposures and adult health outcomes.

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Dutch Hunger Winter Study

This study revealed that prenatal famine exposure affected methylation at a specific gene, IGF2, influencing disease susceptibility in adulthood.

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Methylation and Disease Susceptibility

Altered methylation patterns, especially those resulting from environmental factors, can increase the risk of developing certain diseases later in life.

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Study Notes

Environmental Influences on the Epigenome

  • Epigenetics is the study of heritable changes in gene function that are not attributed to changes in the DNA sequence.

  • Environmental factors influence the epigenome, bringing about changes in gene expression.

Epigenetic Regulators

  • Histone modifications: These include methylation, acetylation, and deacetylation of histones, which impact the accessibility of DNA to transcription factors.

  • DNA methylation: The addition of a methyl group to cytosine bases, typically near guanine (CpG sites). DNA methylation often silences genes. The enzyme DNMT plays a crucial role in this process.

  • Noncoding RNA expression: Small RNA molecules called microRNAs (miRNAs) regulate gene expression by interacting with target messenger RNAs.

Post-Translational Modifications

  • Post-translational modifications (PTMs) are modifications to proteins after their synthesis.

  • These include methylation, acetylation, phosphorylation, glycosylation.

  • PTMs can affect protein function, stability, localization, and interactions with other cellular components, ultimately affecting gene expression.

DNA Methylation Maintenance

  • Immediately after DNA replication, the maintenance methyltransferase enzyme ensures the methylation pattern is copied to both DNA strands.

Chromatin Remodeling - Histone Methylation

  • Histone methylation affects the accessibility of DNA for transcription. Methylation can increase the effects of a modification.

Acetylation

  • Acetylation is the transfer of an acetyl group to nitrogen, a reversible process in nearly all eukaryotic proteins. It is often associated with activation of gene expression.

3-Chromatin Remodeling - Histone Acetylation

  • Histone acetylation and deacetylation are critical for gene regulation. These modifications affect the structure of chromatin, influencing gene expression.

MicroRNAs

  • MicroRNAs (miRNAs) are small RNA molecules (18-24 base pairs) that regulate gene expression by interacting with complementary messenger RNAs (mRNAs). This interaction affects mRNA stability and translation.

  • miRNAs are processed to become functional molecules.

DNA Methylation and Environment

  • Global DNA methylation changes, either loss or gain, have been linked to various environmental exposures.

Gene-Specific Methylation

  • Studies have highlighted DNA methylation at specific genes and links to environmental exposures. This is primarily focused on exposures during prenatal development, but also affecting adult health.

Transcription Factors and Environmental Exposure

  • Environmental factors can trigger changes in transcription factors, influencing DNA methylation at specific locations. This can either result in hypermethylation or hypomethylation at the gene.

Environmental factors that can lead to changes in DNA methylation

  • Dietary factors,
  • Toxins such as arsenic,
  • Pollution (e.g., air pollution)
  • Tobacco smoke,
  • Endocrine disruptors (e.g., BPA)
  • Persistent organic pollutants

What factors are most important in epigenetics research?

  • Environmental mixtures: assessment of complex mixtures of contaminants
  • Sex-specific effects
  • Tissue specificity
  • Stability and functional consequences (long-term effects of methylation)

Conclusion

  • The interplay between genetics, the environment, and epigenetics is dynamic and complex. This complex interplay has implications for understanding the impact of environmental factors on health.

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Environmental Influences on the Epigenome Lecture 7-8 PDF

Description

This quiz explores the fascinating field of epigenetics, focusing on how environmental factors alter the epigenome. Topics include histone modifications, DNA methylation, and post-translational modifications, providing insights into gene expression regulation.

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