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genetics > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

What is a classic epigenetic mark?

A

DNA-methylation : 5-methylcytosine

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2
Q

What is special about 5-methylcytosine

A

Can be propagated across divisions
associated with gene transcription

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3
Q

What are CpG islands?

A

CG dinucleotides enriched at many promoters

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4
Q

How is the nucleosome organized?

A

four histones with 2 copies each (octamere)

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5
Q

What are the core histones?

A

H2A, H2B, H3, H4: H1 is a linker histone (one per nucleosome)

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6
Q

Where does histone - DNA contact take place?

A

Histone fold domain

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7
Q

hat is special about the histone fold domain?

A

Unstructered N-terminal (site of post translational modification)

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8
Q

What do H2A, H2b histones form and what does H3 and H4 histones form?

A

(H2A, H2B) dimers and (H3, H4) tetrameres respectively

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9
Q

What does chormatine folding do?

A

GHene silencing

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10
Q

What is the difference between constitutive heterochromatine and facultative heterochromatine

A

constitutive heterochromatine:
independent of cell type
little transcription
repetetive sequences (structure regions)

facultative heterochromatine:
inactive gene regions
cell type specific
coding regions

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11
Q

What are functions of nucleosomes

A

packaging
signaling
transcription obstacle

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12
Q

What are the two classes of epigenetic regulators

A

chromatine remodelers
chromatine modifiers

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13
Q

What is the role of chromatine modifications

A

development (gene expression patterns) and transcription
signature modifications are essential for genetic processes

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14
Q

where are histones normally modified?

A

N-terminally (histone code are all modifications)

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15
Q

What does lysine acetylationd do?

A

lysine has positive charge, which is removed by acetylation -> eviction of nucleosome and enables transcription

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16
Q

Are epigenetic marks reversible?

A

Yes

17
Q

What are READER domains and how do they work?

A

Site of Post translational modification allow for recruitment and regulation

18
Q

When are histones normally synthesized?

A

During the S-phase

18
Q

What are histone chaperones and what do they do?

A

Prevent histone-DNA aggregation -> bind histones and are specific for histone variants

19
Q

What does the variant H2A.Z do?

A

Marks boundaries of nucleosome-free and nucleosome-containing regions

20
Q

Do histone chaperones use ATP?

A

No

21
Q

Do histone remodelers use ATP?

A

Yes

22
Q

What do histone remodelers do?

A

Can establish spacing between nucleosomes, can grant DNA access, can edit Nucleosomes

23
Q

What happens during transcription elongation?

A

Nucleosomes dissasembled and reassembled: Histone chaperone FACT removes H2A/H2B for RNA Poly II to pass

24
Q

What are Oncohistones?

A

Histone modifications that affect Post translational modification level. Very specific for different tumors

genetics (24 decks)

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