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Mol / Cel Biology > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Epigenetic pathways regulate?

A

Gene activity in a heritable manner without changing the primary nucleotide sequence of DNA.

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2
Q

Epigenetics structure changes are?

A

Changes are stable and reversible.

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3
Q

Crucial epigenetic reprogramming events occurs?

A

During germ cell development and early embryogenesis.

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4
Q

What is epigenomics?

A

Epigenetic changes in the level of whole genome?

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5
Q

Epigenetic events in eukaryotic organisms provides?

A

A more precise and stable control of gene expression and genomic regulation.

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6
Q

Epigenetic traits have a crucial role in?

A

Genomic stability.

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7
Q

What is the environmental epigenetic signal considered as? The one that triggers changes of the cell.

A

Epigenator.

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8
Q

Epigenator will lead to?

A

Activation of initiator.

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9
Q

Epigenetic initiator identifies?

A

Location on a chromosome where epigenetic marks will be established.

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10
Q

Initiator is xxx binding xxx?

A

Initiator is DNA binding proteins, non coding RNAs.

They are DNA sequence specific.

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11
Q

The ability of DNA-binding proteins to bind to specific

DNA sequences commonly results from?

A

Interactions between an α-helix in the DNA-binding

protein domain.

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12
Q

What is ncRNA?

A

Non-coding RNA. Functional RNA molecule
that is transcribed from DNA but not translated into
proteins

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13
Q

Epigenetic related non-coding RNAs are?

A

Short ncRNA

Long ncRNA

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14
Q

What is ncRNAs function?

A

To regulate gene expression at the transcriptional and post-transcriptional level

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15
Q

Short ncRNA -> microRNA. What does microRNA do?

A

Binds to a specific target mRNA with a complementary sequence to induce:
cleavage
degradation
block translation in the context of a feedback mechanismthat involves chromosome methylation

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16
Q

LongRNAs function?

A

Forms complex with chromatin modifying proteins and recruit their catalytic activity to specific sites in the genome

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17
Q

LongRNAs result after the modification and recruition?

A

Modification of chromatin state and influenced

gene expression.

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18
Q

What is DNA methylation?

A

Addition of a methyl group to the 5-carbon of the base cytosine in CpG-islands.

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19
Q

CpG sites are methylated by?

A

One of three enzymes called DNA methyl transferas (DNMTs)

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20
Q

DNA methylation of a gene’s CpG island repress?

A

Gene expression.

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21
Q

Non-CpG cytosine methylation has been identified at a high level in?

A

Stem cells. The loss of this form of methylation may

be critical in the differentiation.

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22
Q

Histone modification is a covalent what?

A

Covalent post-translation modification (PTM) to histone proteins

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23
Q

Which combination affects gene expression, DNA repair, and chromosome condensation?

A

PTM working together regulating the chromatin structure.

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24
Q

Histone protein PTM includes (5)?:

A 
Methylation
Phosphorylation
Acetylation
Ubiquitylation
Sumoylation
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25
Histones structure?
Histone core and a loosely structured N-tail, which protrudes out of the nucleosome.
26
The majority of histones post-translational modification occurs at?
N-terminal tail. Due to their chemical properties, these epigenetic modifications alter the condensation of the chromatin and, as a consequence, the accessibility of the DNA to the transcriptional machinery.
27
Histones can be acetylated on?
Lysine (K) residues. Enzymes regulating histone acetylation consist of the histone acetyltransferases (HATs) and histone deacetylases (HDACs).
28
What does the acetyl groups addition does?
It neutralizes the positive charge of the amino group of the lysine. Leads to decreased affinity between histone tail and negatively charged DNA
29
Histone methylation occurs on?
Both lysine and argenine (R) residues. | This epigenetic modification is associated with both transcribed and silenced genes.
30
Enzymatically, histone methylation is controlled by?
``` Histone methyltransferase (HMTs) as well as by histone demethylases (HDMs) ```
31
Histone phosphorylation occurs on?
Serine (S), threonine (T) and tyrosine (Y) residues. It is most commonly associated with transcriptional activiation. Because Phos and DNA are both negatively charged.
32
Ubiquitination refers to the attachment of?
The 72-amino acid protein ubiquitin to the histone core proteins H2A and H2B. H2A ubiquitination is repressive. H2B is active and repressed genes.
33
Sumoylation - SUMO proteins are?
Roughly 100 amino acids long and added to their targets by specific ligases.
34
Histone sumoylation is a mark of?
Transcriptional repression
35
Acetyl - > Activation | SUMO -> Repression
;)
36
Histone variants affects functionally what?
Chromatin remodelling and histone post-translational modifications.
37
What does nucleosome remodelling refers to?
To the change in the structure of chromatin. The process requires ATP energy imput.
38
Nucleosome remodelling is carried out by?
Enzymes called ATPase's
39
ATPpase's activation can lead to?
Dissambly of nucleosomes. Exchange of histones for variants. Assembly of nucleosomes.
40
What does allelic imbalance means?
The ratio of gene expression levels from each of two alleles in diploid genome is not 1 : 1
41
Why does this allelic imbalance occurs?
Because variants in the DNA sequence causes different level of expression at two gene copies
42
What the heck is monoallelic expression?
Only one of the two copies of a | gene is active, while the other is silent.
43
Monoallelic expression has how many types?
``` Four. Somatic rearrangement. Random allelic silencing or activation. Genomic imprinting. X chromosome inactivation ```
44
In cancer tissues, DNA methylation is reduced or increased?
Reduced. Hypomethylating oncogene promoters, reducing defence against repetitive sequences leading to genome instability and chromosome structural changes. Decreased gene methylation has subsequent effects on transcription.
45
Somatic rearrangement in monoallelic expression?
Changes in DNA organization to produce functional gene at one gene copy, but not other. Random choice of one gene copy.
46
Random allelic silencing or activation in monoallelic expression?
Expression from only one gene copy at chromosomal localization (locus), due to different epigenetic changes. Random choice of one gene copy. Specific cell type.
47
Genomic imprinting in monoallelic expression?
Epigenetic silencing of gene copy in imprinted regions. Imprinted region marked epigenetically according to the parental origin (parent-of-origin mechanism)
48
X chromosome inactivation in monoallelic expression?
Epigenetic silencing of X chromosome linked genes on one female chromosome. Random choice of C chromosome.
49
What does epigenetics study?
How DNA interacts with smaller molecules found within cells, which can active or deactivate genes.
50
In a nutshell what epigenetics can do?
Epigenetic changes can boost or interfere with the trascription of spesific genes.
51
DNA or protein that's wrapped around gets labelled with small chemical tags. The set of all chemical tags that are attached to the genome in a given cell is called?
Epigenome.
52
What does example the methyl group do to the gene?
It inhibits gene expression by interfering the transcription machinery or causing the DNA to coil more tightly, making it inaccessible.
53
Why can epigenetic changes can affect an organism for rest of its life?
Because epigenetic changes can survive cell division.
54
Environmental factors can affect epigenetics, why?
Because the chemical tags that turn genes on and off can be influenced by factors like diet, chemical exposure and medication etc.
55
Example: when skin cells divide, why they are still skin cells?
Epigenetics maintain their tissue identity.
56
Tissue identity depends on?
Which genes are turned on and off.
57
Acetylation of amino acids on histones generally correlates to gene activation. Why?
Acetylation reduces the positive charge of histone tails and repels the from the negatively charged DNA backbone in the packed nucleosome.
58
Lysine and arginine amino acid residues on histone tails can be methylated. Methylation is more complex than acetylation. Its correlation to gene activity depends on?
The context of where the mark is placed.
59
Epigenetic regulation is established and maintained by how many classes of proteins or enzymes?
Three classes. | Readers, writers and erasers.
60
Readers can?
bind either active or repressive marks on chromatin
61
Writers can?
Place either active or repressive marks on chromatin
62
Erasers can?
Remove marks from chromatin.
63
What does initiator translate?
The epigenator signal

Mol / Cel Biology (17 decks)

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