RNA Flashcards

1
Q

In what ways is RNA different from DNA?

A

RNA is shorter
RNA is single stranded (vs ds DNA)
RNA can form secondary loop and stem structures (e.g. tRNA)

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2
Q

What is the most abundant form of RNA in the cell

A

rRNA

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3
Q

RNA is synthesized ___’ to ___’

A

5’ to 3’

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4
Q

Does RNA require a primer?

A

No

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5
Q

What is the function of the beta subunit of RNA polymerase?

A

Contains the catalytic site

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6
Q

What is the function of the sigma subunit of RNA polymerase?

A

Recognizes the promoter region of RNA

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7
Q

Does transcription transcribe the whole genome?

A

No, there are discreet areas that are transcribed.

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8
Q

How do promoters work in eukaryotes?

A

2 sequence elements at -35 and -10

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9
Q

What piece of RNA polymerase recognizes and binds to the promoter region?

A

Sigma subunit

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10
Q

What are the steps of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
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11
Q

What is the committed step of transcription initiation.

A

Moving from a closed promoter to an open complex with 2 open strands. Transcription bubble always 12 bases wide.

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12
Q

RNA almost always starts with a ____.

A

Purine

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13
Q

How long is the RNA-DNA hybrid in the beta subunit of RNA Polymerase?

A

8 bases

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14
Q

What sequence signifies transcription rho-independent termination site?

A

GC-rich palindrome followed by UUU

(a self-complementary sequence!)

UUU forms a hairpin loop

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15
Q

A small fraction of transcription termination is __________.

A

Rho-dependent

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16
Q

How does rifampicin work?

A

It inhibits the formation of the first phosphodiester bond in transcription initiation

17
Q

How is eukaryotic transcription different than prokaryotic?

A
  1. Three polymerases
  2. No sigma subunit
  3. Polymerase-protein interactions govern specificity
18
Q

What does RNA Polymerase I do?

A

Large rRNAs (28s, 18s, 5.8S) in the nucleolus

19
Q

What does RNA Polymerase III do?

A

Transcribes the precursors of small RNAs (tRNAs and 5S rRNAs)

20
Q

What does RNA Polymerase II do?

A

Transcribes the precursors of mRNAs

21
Q

Does RNA Polymerase II have a sigma factor?

A

No! Instead Pol II interacts with specific PROTEINS which bind core promoter regulatory elements

22
Q

What are key features of the eukaryotic promoter?

A

Further from beginning of transcription than prokaryotes

TATA box/basal element (-25)

Additional constitutive elements -40 to -110

Inducible elements -150

23
Q

What do constitutive elements in the eukaryotic promoter do?

A

Govern the RATE of transcription

24
Q

What do inducible elements do?

A

Cause initiation of transcription in response to hormones or very specific environmental stimuli

25
What binding factors must proceed binding of Pol II?
TATA binding protein (TBP), TAF, TFIIA-F
26
What is TFIIH?
A binding factor that phosphorylates Pol II to initiate transcription
27
What type of protein binds to enhancers.
Activators
28
What are the components of the core promoter?
Basal element Constitutive element Inducible element
29
How does chromosome remodeling and histone acetylation/deacetylation affect transcription?
Affect efficiency of transcription initiation
30
Are constitutive elements always on to some degree?
Yes
31
How are death cap mushrooms toxic?
Alpha-amanitin inhibits RNA Pol II in eukaryotes.