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Biol 207 > Topic 7-2 > Flashcards

Topic 7-2 Flashcards

1
Q

eukaryotic DNA is condensed into chromatin structure and is often:

A

inaccesible

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2
Q

regulate access to DNA

A

nucleosome modifications

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3
Q

where do chromatin remodeling complexes bind?

A

DNA sites and reposition nucleosomes

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4
Q

acetylation of histone proteins _______ nucleosomes and makes DNA _______

A

destabilize, accesible

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5
Q

what is the function of chromatin remodelling complexes?

A

to reposition the nucleosomes, allowing transcription factors and RNA polymerase to bind to promoters and initiate transcription

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6
Q

what is the function of acetylation of histone proteins?

A

alters chromatin structure and permits some transcription factors to bind to DNA

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7
Q

what is an example of histone modifications allowing for gene expression?

A

acetylation of histones controlling flowering in arabidopsis thaliana (FLC and FLD genes)

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8
Q

a gene that encodes a deacetylase enzyme

A

flowering locus D (FLD)

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9
Q

what does FLD do?

A

encodes an enzyme that removes acetyl groups adn restores the chromatin structure, allowing flowering

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10
Q

what does FLC do?

A

encodes a regulatory protein that represses flowering

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11
Q

how many types of RNA polymerases do eukaryotes have?

A

three

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12
Q

the promoters of genes trascribed by RNA polymerase II consist of two primary parts:

A

a core promoter and a regulatory promoter

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13
Q

just upstream of the gene and similar to a bacterial promoter

A

core promoter

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14
Q

upstream of the core promoter and has a more varied consensus sequence:

A

regulatory promoter

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15
Q

eukaryotic transcription requires ________ that bind directly to DNA and recruit _______

A

accessory proteins, RNA polymerases

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16
Q

any DNA binding protein that affects the levels of transcription

A

transcription factors (TF)

17
Q

about how many trascription factors are in humans

A

> 1000

18
Q

what do TFs do?

A

bind regulatory promoter sequences and affect transcription by directly or indirectly contacting the basal transcription apparatus

19
Q

general transcription factors and RNA polymerase II make up the:

A

basal transcription apparatus

20
Q

the basal transcription apparatus is sufficient to initiate:

A

minimal levels of transcription

21
Q

transcription is frequently controlled by:

A

DNA binding proteins

22
Q

many types of DNA binding proteins have evolved with functional parts referred to as:

A

domains

23
Q

many types have evolved that share characteristic domains called:

A

motifs

24
Q

what are the five main steps to initiate basal transcription in eukaryotes?

A

1) TFIID binds to the TATA box in the core promoter
2) TFs and RNA pol. II bind to the core promoter
3) transcriptional activator proteins bind to sequences in enchancers
4) DNA loops out, allowing the proteins bound to the enhancer to interact with the basal transcription apparatus
5) transcriptional activator proteins bind to sequences in the regulatory promoter and interact with the basal transcription apparatus through the mediator

25
Q

the TATA-binding protein (TBP) binds to the:

A

minor groove of DNA, straddling the double helix

26
Q

more distant from the gene, but the DNA can loop over allowing interaction with DNA binding proteins and polymerase

A

enhancers

27
Q

once RNA pol. II and general TFs are assembled on the core promoter…

A
  • 11-15 bp of DNA unwinds around the transcription start site
  • open complex: template strand positioned in RNA pol’s active site
  • RNA synthesis begins
28
Q

after the first ~30 nucleotides are polymerized, RNA pol. II will:

A

move off the promoter and proceed downstream to elongate the RNA molecule

29
Q

how many nucleotides of RNA with remain paired with the DNA template strand as transcription progresses downstream?

A

~8

30
Q

molecular structure of RNA pol. II and how it functions during elongation have been revealed through the work of:

A

Roger Kornberg and colleagues

31
Q

what three things happen after RNA pol. II moves downstream

A
  • the DNA double helix enters RNA pol. II through a cleft in the enzyme and unwinds
  • the DNA-RNA duplex is bent at a right angle, which positions the 3’ end of the RNA at the active site of the enzyme
  • new nucleotides are added to the 3’ end of the RNA molecule
32
Q

during eukaryotic termination, RNA pol. I and III have similar mechanisms to:

A

bacteria

33
Q

during eukaryotic termination, RNA pol. II continues to synthesize DNA well past the end of the coding sequence, creating:

A

pre-mRNA

34
Q

pre-mRNA is cleaved at the consensus site, creating:

A
  • mRNA –> protein
  • stil transcribing peice with 5’ hanging
35
Q

binds 5’ hanging end and “eats” its way to the polymerase/transcription –> causes termination

A

exonuclease protein Rat1

Biol 207 (34 decks)

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