Podcast
Questions and Answers
Which of the following epigenetic mechanisms involves the addition of a methyl group to DNA?
Which of the following epigenetic mechanisms involves the addition of a methyl group to DNA?
Most CpG islands in normal human cells are typically methylated.
Most CpG islands in normal human cells are typically methylated.
False
What is the universal methyl donor involved in DNA methylation?
What is the universal methyl donor involved in DNA methylation?
S adenosyl methionine
A cluster of CpG residues often found near gene promoters is known as a __________.
A cluster of CpG residues often found near gene promoters is known as a __________.
Signup and view all the answers
Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
Signup and view all the answers
Which modification enhances transcription by reducing the positive charges on histones?
Which modification enhances transcription by reducing the positive charges on histones?
Signup and view all the answers
Histone deacetylation enhances transcription.
Histone deacetylation enhances transcription.
Signup and view all the answers
What is the effect of methylation on histones?
What is the effect of methylation on histones?
Signup and view all the answers
H3K27me3 is primarily methylated by the methyltransferase called ______.
H3K27me3 is primarily methylated by the methyltransferase called ______.
Signup and view all the answers
Match the following histone modifications with their primary effects:
Match the following histone modifications with their primary effects:
Signup and view all the answers
What is one of the three known mechanisms of epigenetics?
What is one of the three known mechanisms of epigenetics?
Signup and view all the answers
Increased cytosine methylation of the NR3C1 promoter is associated with suicide victims who had no childhood abuse.
Increased cytosine methylation of the NR3C1 promoter is associated with suicide victims who had no childhood abuse.
Signup and view all the answers
What role does the hypothalamic-pituitary-adrenal (HPA) axis play in relation to childhood abuse?
What role does the hypothalamic-pituitary-adrenal (HPA) axis play in relation to childhood abuse?
Signup and view all the answers
Core histones are rich in basic amino acids and have a structure consisting of three α helices connected by two ______.
Core histones are rich in basic amino acids and have a structure consisting of three α helices connected by two ______.
Signup and view all the answers
Which histone modification is associated with gene activation?
Which histone modification is associated with gene activation?
Signup and view all the answers
Match the following histone modifications with their functions:
Match the following histone modifications with their functions:
Signup and view all the answers
What are the possible effects of childhood abuse on NR3C1 mRNA levels?
What are the possible effects of childhood abuse on NR3C1 mRNA levels?
Signup and view all the answers
Histone code refers to the specific modifications of histones that can dictate gene expression.
Histone code refers to the specific modifications of histones that can dictate gene expression.
Signup and view all the answers
What is the main focus of epigenetics?
What is the main focus of epigenetics?
Signup and view all the answers
Epigenetics can explain why identical twins may have different physical traits despite having the same DNA.
Epigenetics can explain why identical twins may have different physical traits despite having the same DNA.
Signup and view all the answers
Who first coined the term 'epigenetics'?
Who first coined the term 'epigenetics'?
Signup and view all the answers
The process by which one parental allele is silenced is known as __________.
The process by which one parental allele is silenced is known as __________.
Signup and view all the answers
Match the following epigenetic concepts with their definitions:
Match the following epigenetic concepts with their definitions:
Signup and view all the answers
What is the length of each base pair in DNA?
What is the length of each base pair in DNA?
Signup and view all the answers
All genes in a genome are expressed equally in every cell type.
All genes in a genome are expressed equally in every cell type.
Signup and view all the answers
What phenomenon can lead to two different eye colors in a single individual?
What phenomenon can lead to two different eye colors in a single individual?
Signup and view all the answers
What is the primary role of the PRC2 complex?
What is the primary role of the PRC2 complex?
Signup and view all the answers
H3K27me3 is associated with active gene promoters.
H3K27me3 is associated with active gene promoters.
Signup and view all the answers
What modification is known for shutting down transcription?
What modification is known for shutting down transcription?
Signup and view all the answers
The enzyme __________ is part of the PRC2 complex that is involved in histone methylation.
The enzyme __________ is part of the PRC2 complex that is involved in histone methylation.
Signup and view all the answers
Match the following chromatin modifications with their biological roles:
Match the following chromatin modifications with their biological roles:
Signup and view all the answers
Which of the following lysine modifications is associated with transcriptional repression?
Which of the following lysine modifications is associated with transcriptional repression?
Signup and view all the answers
Acetylation and phosphorylation are associated with opening chromatin.
Acetylation and phosphorylation are associated with opening chromatin.
Signup and view all the answers
What is the effect of H3K27 trimethylation on developmental genes?
What is the effect of H3K27 trimethylation on developmental genes?
Signup and view all the answers
Which of the following best describes the role of long non-coding RNAs (lncRNAs) in DNA methylation regulation?
Which of the following best describes the role of long non-coding RNAs (lncRNAs) in DNA methylation regulation?
Signup and view all the answers
Histone acetyltransferases (HATs) are responsible for removing acetyl groups from histones.
Histone acetyltransferases (HATs) are responsible for removing acetyl groups from histones.
Signup and view all the answers
What is the hallmark of the epithelial-mesenchymal transition (EMT) process?
What is the hallmark of the epithelial-mesenchymal transition (EMT) process?
Signup and view all the answers
The interaction of Xist RNA with the X chromosome results in ______.
The interaction of Xist RNA with the X chromosome results in ______.
Signup and view all the answers
Match the following enzymes or complexes to their functions:
Match the following enzymes or complexes to their functions:
Signup and view all the answers
What effect do acetylated lysine residues have on histones?
What effect do acetylated lysine residues have on histones?
Signup and view all the answers
Random X-inactivation in calico cats is based on genetic inheritance.
Random X-inactivation in calico cats is based on genetic inheritance.
Signup and view all the answers
What role does the Polycomb Repressive Complex 2 (PRC2) play in gene regulation?
What role does the Polycomb Repressive Complex 2 (PRC2) play in gene regulation?
Signup and view all the answers
Study Notes
Epigenetics Introduction
- Epigenetics is the study of heritable changes in gene expression or the phenotype.
- These changes occur without alterations to the underlying DNA sequence.
- Epigenetic changes are influenced by factors beyond DNA sequence, such as environment.
- The term "Epi" means on top of/above.
- Epigenetics was first coined by C.H. Waddington.
- He used it to explain cell differentiation beyond genetics.
- Waddington's work included genetic assimilation.
- This involved the acquisition of inherited characteristics through environmental influences.
- An example of Waddington's work was the crossveinless trait in Drosophila.
Questions Related to Epigenetics
- Different adult stem cells have specific fates.
- Myoblasts form muscle and keratinocytes form skin cells.
- Identical twins can have different hair and eye colors due to epigenetic changes.
- Identical twin littermates can have different coat colors because of epigenetic changes.
- Imprinting can silence one parental allele.
- X-inactivation is a type of dosage compensation.
Packing DNA into Chromatin
- Each base pair in DNA is 0.34 nm long.
- The human body has billions of base pairs per cell.
- A typical cell has 2 meters of DNA, yet the nucleus measures only 2-10 μm.
- Humans have approximately 50 trillion cells.
- The DNA in a human body is 100 trillion meters long.
- The distance between the Sun and Earth is 150 billion meters.
- Each person's DNA could stretch from Earth to the Sun and back over 300 times.
- Chromatin compacts DNA within the nucleus.
Nucleosomes
- The nucleosome is the fundamental unit of chromatin.
- It is composed of histone octamer and 147 base pairs of DNA.
- Histone proteins include H2A, H2B, H3, H4 (core histones) and H1 (linker histone).
- It compacts DNA structure within the nucleus.
- It associates with transcription.
Mechanisms of Epigenetics
- There are three main mechanisms of epigenetics:
-
- DNA methylation
-
- Histone modification
-
- Non-coding RNA
DNA Methylation and Histone Modifications
- DNA methylation involves methyl groups attached to specific DNA bases.
- This often silences gene activity.
- Histone modifications include various molecules attaching to histone tails.
- These modifications alter the activity of the DNA around histones.
Cytosine Methylation
- Cytosine methylation involves adding a methyl group to cytosine bases in DNA.
- Methylation commonly occurs at CpG sites.
- The universal methyl donor is S-adenosylmethionine (SAM).
CpG Islands
- CpG islands are clusters of CpG sites often found near gene promoters.
- A CpG island should have at least 200 base pairs and over a 60% GC content.
- They are important for gene regulation.
- Most CpG islands are unmethylated in normal cells.
- They play a role in many processes, including cancer.
Methylation Patterns in Diseases (e.g., Cancer)
- Abnormal methylation patterns are associated with diseases like cancer.
- This includes both global hypomethylation and focal hypermethylation of genes.
- Dysregulation of tumor suppressor genes (TSGs) and oncogenes can be affected.
Progressive Alterations in DNA Methylation in Cancer
- Cancer development is associated with gradual changes in DNA methylation.
- This encompasses shifts from global hypomethylation to regional hypermethylation.
- This process involves an accumulation of epigenetic abnormalities.
CpG Island Methylation
- CpG island methylation is a stable, heritable, and detectable epigenetic signal that has important roles in normal development and disease.
- CpG methylation patterns are readily observed and change in step and through the progression in disease.
DNA Methylation in Stem Cells
- DNA methylation differentiates totipotent embryonic stem cells from unipotent adult stem cells. The methylation patterns are different and distinguishable.
How Methylation Inhibits Transcription
- Methylation may inhibit the binding of regulatory factors to the DNA promoter region.
- Methylation can prevent the binding of activator proteins to enhancer elements.
- Methylation can cause proteins called methyl-CpG-binding proteins (MBPs) to bind.
- These proteins recruit other proteins that then rearrange the chromatin to a less accessible conformation (often repressed).
Establishment and Maintenance of Cytosine Methylation
- De novo methylation occurs via DNMT3a and DNMT3b enzymes.
- Maintenance methylation is aided by DNMT1.
- These enzymes are vital for the regulation of epigenetic modifications.
Bisulfite Sequencing
- Bisulfite treatment is a DNA sequencing method for detecting methylation patterns.
- The treatment will convert cytosine to uracil.
- 5-methylcytosine nucleotides are unaffected.
IncRNA and Epigenetics
- Non-coding RNAs, including IncRNAs, influence epigenetics.
- IncRNAs are associated with DNA methylation and histone modifications, and thereby regulate transcription.
- IncRNAs can either activate or repress transcription.
Chromatin Structure
- Euchromatin: Active genes, accessible DNA, light-staining, open conformation.
- Heterochromatin: Silent genes, inaccessible DNA, dark-staining, closed conformation.
Core Histones
- Core histone proteins (H2A, H2B, H3, H4) are highly conserved and enriched in basic amino acids.
- These are important for DNA packaging.
Histone Modifications
- Histone modifications (methylation, acetylation, phosphorylation, ubiquitination, sumoylation, and other modifications) regulate gene expression.
Methylation of Histone H3-K27
- H3K27 methylation is associated with gene silencing
- The enzyme EZH2 and Polycomb Repressive complexes (PRCs) mediate this methylation.
Chromatin Modifications
- Various modifications are associated with specific biological processes.
- These include methylation of cytosine (DNA), acetylation or phosphorylation of lysines (histones), and methylation of arginines (histones).
Maternal Behavior and Epigenetics
- Maternal behaviors affect methylation patterns in offspring's brains.
- Attentive or inattentive mothering can affect epigenetic modifications in offspring brains.
Rainbow and Copycat Cats
- Random X chromosome inactivation patterns result in distinctive coat patterns.
- Coat coloring in calico cats due to stochastic inactivation.
Xist RNA and Epigenetics
- Xist IncRNA functions in cis to silence the X chromosome.
- Xist interacts with transcriptional regulators via the chromatin.
Histone Modifications and Modifiers
- Histone modifiers include:
- Writers (acetylases, methylases, phosphorylases)
- Readers (proteins binding to the marks)
- Erasers (deacetylases, demethylases, phosphatases)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge of epigenetic mechanisms, particularly DNA methylation. This quiz covers key concepts such as CpG islands, histone modifications, and the roles of various methyltransferases. Dive deep into the effects of methylation and its implications on gene expression and behavior.