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Questions and Answers
What role does DNA methylation play in the X chromosome of females?
What role does DNA methylation play in the X chromosome of females?
How does histone acetylation affect histones and transcription?
How does histone acetylation affect histones and transcription?
What is somatic mosaicism, and how does it affect traits?
What is somatic mosaicism, and how does it affect traits?
Which of the following best describes the effect of DNA methylation on gene transcription?
Which of the following best describes the effect of DNA methylation on gene transcription?
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During which phase of development does X chromosome inactivation occur?
During which phase of development does X chromosome inactivation occur?
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What is the result of a female inheriting one normal allele and one disease allele on an X chromosome?
What is the result of a female inheriting one normal allele and one disease allele on an X chromosome?
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What are histones, and what role do they play in relation to DNA?
What are histones, and what role do they play in relation to DNA?
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What happens to segments of DNA when they are tightly bound to histones?
What happens to segments of DNA when they are tightly bound to histones?
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What is the primary cause of Prader-Willi syndrome?
What is the primary cause of Prader-Willi syndrome?
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Which syndrome is characterized by severe intellectual disability and seizures?
Which syndrome is characterized by severe intellectual disability and seizures?
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What is the common congenital feature of Beckwith-Wiedemann syndrome?
What is the common congenital feature of Beckwith-Wiedemann syndrome?
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What percentage of Russell-Silver syndrome cases are linked to imprinting abnormalities on chromosome 11p15.5?
What percentage of Russell-Silver syndrome cases are linked to imprinting abnormalities on chromosome 11p15.5?
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In what way does maternal uniparental disomy affect Beckwith-Wiedemann syndrome?
In what way does maternal uniparental disomy affect Beckwith-Wiedemann syndrome?
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What is the impact of in utero ethanol exposure on neural stem cells?
What is the impact of in utero ethanol exposure on neural stem cells?
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How does PTSD affect gene expression in neural pathways?
How does PTSD affect gene expression in neural pathways?
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What was a consequence for individuals conceived during the starvation in the Netherlands in 1943?
What was a consequence for individuals conceived during the starvation in the Netherlands in 1943?
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What role does histone methylation play in binding strength to DNA?
What role does histone methylation play in binding strength to DNA?
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How do protamines differ from histones in terms of DNA compaction?
How do protamines differ from histones in terms of DNA compaction?
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What type of genes escape epigenetic silencing and remain active in all or nearly all cells?
What type of genes escape epigenetic silencing and remain active in all or nearly all cells?
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Which of the following best describes monoallelic gene expression?
Which of the following best describes monoallelic gene expression?
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What hypothesis explains the genetic conflict between mothers and fathers in offspring resource allocation?
What hypothesis explains the genetic conflict between mothers and fathers in offspring resource allocation?
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What characterizes totipotent cells in an early embryo?
What characterizes totipotent cells in an early embryo?
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In genomic imprinting, what percentage of autosomes typically show imprinting?
In genomic imprinting, what percentage of autosomes typically show imprinting?
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What effect does the expression of imprinted genes from the mother have in offspring?
What effect does the expression of imprinted genes from the mother have in offspring?
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What have studies suggested about the offspring of individuals affected by epigenetic modifications?
What have studies suggested about the offspring of individuals affected by epigenetic modifications?
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What is a proposed characteristic of senescence in relation to epigenetics?
What is a proposed characteristic of senescence in relation to epigenetics?
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What effect does long-term use of metformin appear to have on lifespan?
What effect does long-term use of metformin appear to have on lifespan?
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How do tumor cells generally differ from normal cells in terms of methylation?
How do tumor cells generally differ from normal cells in terms of methylation?
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What is the role of histone deacetylases in chromatin activity?
What is the role of histone deacetylases in chromatin activity?
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What approach has shown promise for detecting certain types of cancer?
What approach has shown promise for detecting certain types of cancer?
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What is a characteristic of epigenetic modifications?
What is a characteristic of epigenetic modifications?
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What has 5-Azacytidine been used for in a therapeutic context?
What has 5-Azacytidine been used for in a therapeutic context?
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Study Notes
Epigenetics and Disease
- Epigenetics involves modifications to gene expression without changing the underlying DNA sequence.
- These modifications can be heritable and influence health and disease.
- Module 2 learning objectives focus on gene influence on body structure and function, and how gene defects lead to diseases.
Epigenetics
- Modifications are not part of the nucleotide sequence but are passed down during somatic cell division and gamete production.
- These processes control how genes produce phenotypes.
- This includes DNA methylation, histone post-translational modifications, and RNA-based mechanisms.
DNA Methylation
- In females, the inactive X chromosome has high methylation levels.
- Active X chromosomes have less methylation.
- Densely methylated DNA is typically not actively transcribed.
- Epigenetic inactivation of one X chromosome happens during early embryonic development.
- The choice of which X to silence is random and independent in each cell.
- If there are different active alleles in different cells, those cells can have distinct traits.
- Females with a disease allele at a gene on the X chromosome tend to have milder symptoms because one of their X chromosomes is inactivated.
Histone Modification
- Histones are positively charged proteins that wrap DNA.
- These proteins influence DNA condensation in the cell.
- When DNA is densely wrapped, it's called heterochromatin.
- Loosely wrapped DNA is euchromatin.
- Loose wrapping allows transcription factors to access and use the DNA for mRNA production.
- Histone modification is important for cell development.
- Histone acetylation diminishes the positive charge, reducing binding to DNA.
- Methylation can either increase or decrease binding strength.
- Mutations in genes coding for histone modifying proteins are linked to diseases like congenital heart disease.
- Protamines can enable sperm DNA compaction at a higher level than achieved by histones.
- Specific histone modifications improve DNA movement. Changes affect fertility in males.
Epigenetics and Human Development
- Totipotent cells in the early embryo can differentiate into any cell type.
- All cells in an organism have the same genetic makeup.
- Epigenetic information differentiates the functions of differentiated somatic cells.
- Housekeeping genes play a critical role cell function maintenance and are not silenced.
Genomic Imprinting
- Biallelic means both parental copies contribute to the phenotype.
- Monoallelic means only one parental copy is expressed.
- Both maternal and paternal copies are involved in traits but can be influenced in some cells by one copy.
- Imprinting happens in about 1% of autosomes.
- Genetic conflict hypothesis suggests that offspring development interests aren't always aligned. The mother's interest is often to provide child with sufficient resources for long-term survival; the father's interest is to ensure child's present survival.
- Imprinted genes can influence offspring growth.
- The critical phenotype of diseases dependent on which parent transmitted the mutation.
Prader-Willi and Angelman Syndromes
- These imprinting syndromes are due to a deletion in chromosome 15.
- Prader-Willi is caused by deletion on the paternal chromosome, resulting in symptoms such as short stature, hypotonia, etc.
- Angelman syndrome results from a deletion on the maternal chromosome and causes intellectual disability, seizures, etc.
Beckwith-Wiedemann Syndrome
- Observable at birth due to large size, hypoglycemia, big tongue, etc.
- Risk for Wilms tumor and hepatoblastoma.
- Caused by uniparental disomy of chromosome 11.
- This means the child inherits two copies of chromosome 11 from one parent and zero from the other.
- The syndrome is different than Prader-Willi and Angelman due to over expression of a gene product instead of deletion.
Russell-Silver Syndrome
- Characterized by growth retardation, proportionate short stature with leg length differences, and a triangular-shaped face.
- Imprinting abnormalities on chromosome 11p15.5 cause 1/3 of cases.
- Maternal uniparental disomy causes another 10%.
Epigenetics in Cognitive Development and Mental Health
- In utero exposure to ethanol can negatively affect the differentiation of neural stem cells which shows up as dense methylation.
- Children raised in poverty display specific serotonin receptor methylation patterns.
- PTSD alters key neural pathway gene expression and methylation, affecting symptoms.
- Autism is associated with altered DNA methylation.
Epigenetics and Nutrition
- The Dutch Hunger Winter in 1943 affected pregnant women and their children via fetal effects, impacting obesity and diabetes risks.
Epigenetics and Aging
- MZ twins show methylation differences even with similar lifestyles, indicating environmental factors play a role.
- Mice show increased hydroxymethylcytosine levels with age.
- Senescence could potentially be an epigenomic process.
- Metformin may extend lifespan in some contexts.
Epigenetics and Cancer
- Tumor cells often have global decrease of methylation.
- Epigenetic screening is a tool for spotting cancers (bladder, lung, prostate).
Treatment of Epigenetic Disease
- Epigenetic modifications are sometimes reversible.
- DNA demethylating agents like 5-azacytidine are used for diseases such as leukemia/myelodysplasia.
- Histone deacetylase inhibitors can decrease chromatin compaction, promoting cell division reduction in cancers like breast and prostate.
- miRNA therapies modify specific genes for cancer treatment.
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Description
Explore the fascinating world of epigenetics and its implications for disease in this Module 2 quiz. Understand how gene expression is modified without altering the DNA sequence and how these changes can be inherited, influencing health outcomes. Delve into concepts like DNA methylation and their roles in phenotypes and disease mechanisms.
