Lecture 28 - Transcription and RNA Processing Flashcards

1
Q

what are 3 major cellular RNA functions?

A
  1. messenger RNAs (mRNA)
  2. transfer RNAs (tRNA)
  3. ribosomal RNAs (rRNA)
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2
Q

where are all RNAs transcribed from?

A

DNA templates by RNA polymerases (RNAP)

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3
Q

where are RNAs synthesized in eukaryotes?

A

cell nucleus

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4
Q

where are RNAs synthesized in prokaryotes?

A

cytosol

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5
Q

what are the 3 stages of transcription?

A
  1. initiation
  2. termination
  3. termination
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6
Q

what is a barrier to transcription?

A

the packaging of eukaryotic DNA into chromatin

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7
Q

where is transcription regulated?

A

in all cells

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8
Q

what do sigma factors do?

A

direct bacterial RNA polymerase to promoters

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9
Q

where do sigma factors bind?

A

to specific sequences that define bacterial promoters

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10
Q

can sigma factor activity be regulated?

A

yes, in many ways

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11
Q

what is the sigma unit of the RNA polymerase?

A

the specificity filter

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12
Q

how does the sigma subunit work?

A

different sigma associate with the other subunits in the polymerase to search for the preferred promoter sequence

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13
Q

in promoter binding what happens once the promoter region has been recognized?

A

sigma unbinds + core polymerase stays bound + processive

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14
Q

what does eukaryotic RNA polymerases require?

A

general transcription factors for promoter recognition

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15
Q

what are eukaryotic promoters often defined by?

A

TATA box + other core promoter elements

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16
Q

how does transcription proceed?

A

highly processive manner

17
Q

what are elongation factors?

A
  • they suppress the pausing of transcription

- rescue stalled polymerase enzymes

18
Q

what must happen to nucleosomes during elongation?

A

nucleosomes must be removed from the path of elongating polymerase for transcription to proceed

19
Q

what are 2 types of termination in prokaryotic transcription?

A
  1. Rho-independent

2. Rho-dependent

20
Q

what happens in Rho-independent termination?

A
  • G:C pairs form stable stem-loop structure

- terminator causes transcript to unbind from the bubble

21
Q

rho works like a _____

A

helicase

22
Q

how are prokaryotic genes organized?

A

into operons

23
Q

in bacteria cells, several ____ are often expressed ____

A

protein-coding genes

together

24
Q

what are operons?

A

protein-coding genes that are often expressed together

25
Q

what type of proteins do genes in the operon encode?

A

proteins that have related functions

26
Q

what is the expression of the operon regulated by?

A

repressor proteins

27
Q

where do repressor proteins bind?

A

to the operator region in the operon

28
Q

what is the difference between protein-coding genes in eukaryotes and prokaryotes?

A

-protein-coding genes in eukaryotes are always expressed individually

29
Q

what are transcribed mRNAs called?

A

pre-mRNAs because they undergo further processing before leaving the cell nucleus

30
Q

what are the 2 parts of transcribed mRNAs?

A
  • 3’ poly (A) tail

- 5’ capping

31
Q

what does splicing do?

A

remove introns