Cycle 11 Workshop Flashcards
Explain:
The meaning of epigenetics
- “Epi-“ = “on top”
- “Genetics” = “genomic sequence”
- Tells us that it is something on top of our genomic sequence
Define:
Epigenetics
The study of changes in gene expression caused by mechanisms other than changes in the underlying DNA sequence
What is “on top” in epigenome?
Tags
* Methyl, acetyl groups
* Yellow blobs on top of genomic sequence
Differentiate between genome and epigenome
- Genome: Consists of the DNA sequence
- Epigenome: All the tags on top of the DNA sequence
True or False:
Tags are placed randomly on genome
False, tags are put on specific places?
- Where are methyl tags placed?
- Where are acetyl tags placed?
- SPECIFIC cytosine, part of DNA
- SPECIFIC lysine, part of histones
- What is cytosine?
- What is lysine?
- A nucleobase
- An amino acid (K, for short)
True or False:
Epigenetic tags are dynamic
True, they can be turned on and off
What does tagging in epigenome do?
Controls gene expression
* Like the edits in an essay
* Can tell you how to read the essay
What is turning on/off the epigenome tags?
Your life experiences
Define:
Behavioural genetics
The study of how epigenetic alterations induced by experience and environmental stress may affect animal behaviour
True or False:
People undergoing similar life experiences have different epigenomes
False, they have similar epigenomes
Why is DNA negatively charged?
Phosphate backbone
Can monozygotic twins have different epigenomes?
Yes, they have the same genomes but can have different epigenomes
What are histones positively charged?
Contains amino acid lysine
True or False:
There is an attraction between histones and DNA
True
What is it called when eukaryotic DNA and histone protein attract?
Nucleosome
How is it determined if a gene is transcribed?
How tightly DNA is wrapped around the Histone Proteins
Compare:
Euchromatin vs. Heterochromatin
Euchromatin
* Open form
* CAN transcribe
Heterchromatin
* Closed form
* CANNOT transcribe
Where do methylation patterns occur?
Only occurs on the cytosine at CpG regions
State enzymes involved in methylation and what results from it
- DNA Methyltransferase (DNMT)
- DNMT3A, DNMT3B for de novo DNA
- DNMT1 for maintenance
- INACTIVATES transcription
State the enzymes involved in demethylation and what results from it
- Ten-Eleven Translocation (TET)
- ACTIVATES transcription
True or False:
Tags are inheritable
True
What does transgenerational epigenetic inheritance imply?
Means that tags are stable, they are maintained
True or False:
Newly synthesized strands are initially methylated
False, they are initially unmethylated
Describe:
DNA methylation process
- DNMT3A and DNMT3B add methyl groups to de novo (new) DNA
- Newly synthesized strand has non-methylated cytosines but the parent strands maintain the same methylation pattern as before replication began
- DNMT1 recognizes hemi-methylated DNA and does methylation maintenance (methylate the cytosines in the new strand
What is the the purpose of DNMT1?
Recognizes hemi-methylated sites at CpG islands
State the enzymes involved in acetylation and what results from it
- Histone Acetyltransferases (HATs)
- Euchromatin (open)
- INCREASES transcription
State the enzymes involved in deacetylation and what results from it
- Histone Deacetylases (HDACs)
- Heterochromatin (close)
- DECREASES transcription
True or False:
Adding an Acetyl group to Lysine changes Lysine’s charge from positive to negative
False, it changes the charge from positive to neutral
What do HATs do?
- Acetylate lysine residues to remove positive charges
- Reduces affinity between DNA and histones
- Promoter is more accessible to RNA polymerase and transcription factors
Define:
Epigenetic drift
Describes how the epigenome changes as we age
* E.x. Twins will have the same genome at birth, but as they grow, their epigenomes will begin to differ depending on each of their lifestyles
True or False:
Epigenome is incredibly sensitive to envrionmental stimuli
True
Do early life experiences lead to inheritable, long term epigenetic effects on gene expression? Or does life experiences later in life?
Early in life
What do DNMT inhibitor drugs do?
- Prevents DNA methylation
- Allows for expression of certain genes
How can epigenetics be utilizaed in cancer treatment?
- Some tumor suppressor genes in cancer cells are hypermethylated
- DNMT inhibitor inhibits methylation
- Thus activates tmour suppressor gene
How do we edit epigenome with precision?
CRISPR with dead Cas9
Describe:
CRISPR in epigenetics
- Dead Cas9 (dCas9), which can’t cut DNA is used
- Guide RNA recruited to target by Cas9
- dCas9 is fused to epigenetic enzyme
- Results in either demethylation or methylation at targeted sites
What produces your epigenetic clock?
Methylome
What does the epigenetic clock do?
Used a biomarker for diseases
Tells you probability that you will develop a specific disease
Define:
Chronological age
Calendar age (years since birth)
Define:
Biological age
Influenced by your epigenome
Define:
Epigenetic age acceleration
Biological age is older than chronological age (body ages faster due to epigenome)
True or False:
Epigenetics are more correlated with health than SNPs are
True
