Human Genetics > Topic 9 - Epigenetics > Flashcards

Topic 9 - Epigenetics Flashcards

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1
Q

What is epigenetics?

A

Heritable changes in gene expression without changing DNA sequence

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2
Q

What does epigenetics affect?

A

Gene expression and phenotype

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3
Q

What are the main epigenetic mechanisms?

A

DNA methylation and histone modification

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4
Q

What is an epigenetic state?

A

A stable pattern of gene expression passed through cell divisions

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5
Q

What are the three components of epigenetic pathways?

A

Epigenator initiator maintainer

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6
Q

What is an epigenator?

A

External signal that triggers epigenetic change

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7
Q

Give examples of epigenators

A

Differentiation signals, Temperature variations, experiences and sex

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8
Q

What is an epigenetic initiator?

A

Molecule that establishes epigenetic changes

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9
Q

What do initiators do?

A

Cause histone or DNA modifications

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10
Q

What is an epigenetic maintainer?

A

Mechanism that preserves epigenetic state across divisions

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11
Q

What do maintainers do?

A

Maintain chromatin structure over generations via i) DNA Methylation ii) Histone Modification iii) Non-coding RNA-induced gene silencing

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12
Q

What enzyme maintains DNA methylation?

A

DNA methyltransferase (DNMT)

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13
Q

What does DNMT do?

A

Adds methyl groups to cytosine at specific regions of DNA

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14
Q

What is 5mC?

A

5 methylcytosine

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15
Q

What is the effect of cytosine methylation (5mC)?

A

Long term gene silencing

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16
Q

What is the role of Histone Acetyltransferases (HATs)?

A

Acetylate histones to form euchromatin

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17
Q

What is the role of Histone Methyltransferases (HMTs)?

A

Methylate histones to form heterochromatin

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18
Q

How are epigenetic marks preserved during replication?

A

Enzymes associate with PCNA during DNA replication

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19
Q

What is PCNA?

A

Replication factor that helps maintain epigenetic marks

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20
Q

What is a nucleobase?

A

Nitrogenous base without sugar

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21
Q

What is a nucleoside?

A

Base plus sugar

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22
Q

Cytosine vs cytidine?

A

Cytosine is base cytidine is nucleoside

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23
Q

Adenine vs adenosine?

A

Adenine is base adenosine is nucleoside

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24
Q

What is dosage compensation?

A

Balancing gene expression between sexes

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25
How do mammals achieve dosage compensation?
By inactivating one X chromosome
26
What is X inactivation?
Epigenetic silencing of one X chromosome
27
What is a Barr body?
Inactive X chromosome
28
Why is X inactivation necessary?
Females have two X chromosomes
29
What is the result of X inactivation?
Only one X is active per cell
30
Is X inactivation random?
Yes in each cell
31
What is Xi?
Inactive X chromosome
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What is Xa?
Active X chromosome
33
Who discovered X inactivation?
Mary Lyon
34
What is mosaicism?
An organism composed of cells with identical DNA but different patterns of gene expression due to epigenetic modifications
35
Why do females show mosaicism?
Random X inactivation
36
Give an example of mosaicism
Sweat gland expression patterns
37
What is Xist?
Long non coding RNA that silences X chromosome
38
Where does Xist bind?
Binds to the inactive x-chromosone
39
What does Xist do?
Coats the X chromosome and silences it
40
What triggers X inactivation?
Expression of Xist RNA
41
What is Tsix?
RNA that opposes Xist
42
What is Xist Tsix antagonism?
Balance between activation and silencing of X
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What proteins are recruited by Xist?
Polycomb Repressive Complex PRC
44
What is PRC1?
Adds ubiquitin to histone H2A
45
What is PRC2?
Adds methyl groups to histone H3
46
What is the role of PRCs?
Maintain chromosome wide silencing
47
What type of regulation is X inactivation?
Epigenetic
48
What level of regulation is X inactivation?
Whole chromosome
49
What is an epigenator example related to sex?
Female vs male
50
What does the Y chromosome do?
Controls sex differentiation
51
Why are XXX and XX phenotypes similar?
Only one X is active
52
What is the effect of environmental epigenators?
They alter gene expression patterns
53
What is synaptic plasticity?
Changes in neural connections
54
How is epigenetics linked to memory?
Epigenetic changes affect learning and memory formation
55
What hormone is involved in stress response?
Cortisol
56
What does cortisol do?
Releases energy during stress
57
What happens if cortisol levels stay high?
Negative health effects
58
What is the GR gene?
Gene that encodes glucocorticoid receptor
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What does GR protein do?
Binds cortisol and shuts down stress response
60
Where does cortisol act in brain?
Hippocampus
61
What happens when cortisol binds GR?
Stops stress response
62
Why are high GR levels beneficial?
Faster stress recovery
63
What increases GR expression?
Maternal care licking grooming
64
What is NGFI A?
Transcription factor that activates GR gene
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What does NGFI A do to methylation?
Prevents methylation of GR gene
66
What happens if GR gene is methylated?
Reduced expression of GR
67
What is the effect of low GR levels?
Poor stress regulation
68
What does maternal care do epigenetically?
Reduces methylation increases GR expression
69
What is the key takeaway from rat experiment in environment?
Environment can change gene expression via epigenetics
70
What type of regulation is seen in rat experiment?
DNA methylation changes
71
What is the NRC31 gene?
Gene encoding glucocorticoid receptor
72
What happens when GR levels are high?
Stress shuts off faster
73
What happens when GR levels are low?
Stress persists longer
74
What is the connection between epigenetics and environment?
Environment can permanently alter gene expression
75
What is the main idea of epigenetic inheritance?
Gene expression patterns can be passed down without DNA changes
76
What are two examples of Uniparental Disomy?
Prader-Willi Syndrome: happens if both copies of chromosome #15 are inherited from the mother. Angelman Syndrome: happens if both copies of chromosome #15 are inherited from the father.
77
What is the IGF2 gene?
A gene that provides instructions for making insulin-like growth factor 2.
78
What protein does IGF2 produce?
Insulin-like growth factor 2 (IGF2 protein).
79
What is the main role of IGF2 before birth?
It plays an essential role in growth and development before birth.
80
What does IGF2 promote in cells?
Growth and division (proliferation) of cells in many tissues.
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What additional function does IGF2 have?
Metabolic functions such as energy use and storage.
82
What is genomic imprinting in IGF2 (normal conditions)?
Only one parental copy of the gene is active.
83
Which IGF2 allele is active under normal conditions?
The paternal (father’s) copy.
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Which IGF2 allele is inactive under normal conditions?
The maternal (mother’s) copy.
85
What modification is associated with the active IGF2 allele?
Acetylation.
86
What modification is associated with the inactive IGF2 allele?
Methylation.
87
Why is IGF2 important in development?
It regulates cell growth, division, and metabolism during early development.
88
What are transgenerational effects?
Epigenetic modifications that are passed on to offspring
89
What is the epigenome?
A set of reversible chemical modifications on DNA and histones that control gene expression without altering the DNA sequence.
90
How does acetophenone demonstrate transgenerational epigenetic inheritance?
Mice conditioned to fear acetophenone produced offspring with increased sensitivity to the odor due to inherited epigenetic changes (e.g., altered DNA methylation) in sperm, without changes in DNA sequence.
91
How does PCOS demonstrate epigenetic inheritance?
Changes in methylation alter gene expression and can be passed to offspring without changing DNA sequence.
92
What is genomic imprinting?
When your body only uses one copy of a gene depending on which parent it came from controlled by epigenetic modifications (e.g., DNA methylation).
93
Why do imprinted genes only have one allele silenced?
One of there genes is methylated thus you only inherit one allele from one parent. Tend to be involved in growth/metabolism
94
What is maternal imprinting?
Express only parental allele (from dad) since mom's was silenced
95
What is paternal imprinting?
Express only the maternal allele (from mom) since dad's was silenced
96
What is Igf2?
Promotes growth, but must bind Igf2 receptor (Igf2R)
97
What is Igf2R?
Suppresses growth by controlling the influence of Igf2
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