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cell proliferation > transcription and splicing > Flashcards

transcription and splicing Flashcards

1
Q

how many base pairs of DNA sequence does the human genome contain

A

3 billion

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2
Q

how must the expression of genes be regulated

A

both spatially and temporally

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3
Q

how many classes of RNA polymerase do eukaryotic cells contain

A

3

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4
Q

what are the 3 types of RNA polymerase

A

RNA polymerase I-III

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5
Q

what does RNA polymerase I do

A

transcribes ribsomal RNA in the nucleus - components of ribosomes (rRNA)

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6
Q

what does RNA polymerase II do

A

transcribes messenger RNA (mRNA: protein coding) in the nuceloplasm

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7
Q

what does RNA polymerase III do

A

transcribes 5S rRNA, tRNA and other small RNAs in the nuceloplasm (translation of mRNA into protein)

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8
Q

how frequent are histones on a DNA strand

A

every 110 base pairs

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9
Q

how many subunits do eukaryotic RNA polymerases contain

A

~12

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10
Q

what does the largest subunit in RNA polymerase II have

A

a carboxy-terminal domain (CTD) consisting of multiple repeats of a heptamer

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11
Q

what do promoter regions do

A

recruit RNA polymerase and opens DNA

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12
Q

what does 5’ UTR signal for

A

initiation of translation

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13
Q

what is transcription

A

the copying of a DNA strand onto an RNA strand

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14
Q

what does 3’ UTR contain

A

translational termination signals

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15
Q

what are the 4 stages of transcription

A

template recognition, initiation, elongation and termination

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16
Q

what occurs during template recognition

A

RNA polymerase binds to duplex DNA, and DNA is unwound at the promoter

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17
Q

what happens during initiation

A

chains of 2-9 bases are synthesized and released

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18
Q

what happens during elongation

A

RNA polymerase synthesizes RNA, unwound region moves with RNA polymerase, RNA polymerase reaches the end of the gene

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19
Q

what happens during termination

A

RNA polymerase and RNA are released

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20
Q

what must happen before RNA polymerase can bind to the promoter

A

chromatin must be opened

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21
Q

what are basal transcription factors

A

transcription factors required by RNA polymerase II to form the initiation complex at all RNA polymerase II promoters - factors are identified as TFIIX (X=letter)

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22
Q

what are coactivators

A

factors required for transcription that do not bind DNA, but are required for DNA-binding activators to interact with the basal TFs

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23
Q

what is a TATA box and what does it consist of

A

a common component of RNA polymerase II promoters which consist of an A-T-rich octamer located ~25bp upstream of the startpoint

24
Q

what is the TATA-binding protein (TBP)

A

a component of the positioning factor that is required for each type of RNA polymerase to bind its promoter

25
Q

what is the basal TF for RNA polymerase II

A

TFIID

26
Q

what is initiation followed by

A

promoter clearance and elongation

27
Q

which basal TFs are required to melt DNA to allow polymerase movement

A

TFIIE and TFIIH

28
Q

what is required for promoter clearance and elongation to begin

A

phosphorylation of the C-terminal domain (CTD) or RNA polymerase II

29
Q

what are enhancer regions

A

sequences which transcription factors bind to

30
Q

where are enhancer regions located

A

can be upstream OR downstream from the promoter

31
Q

what do enhancers form complexes of

A

activators that interact with the promoter

32
Q

what are reppressors

A

a protein that inhibits expression of a gene, may act to prevent transcription by binding to an enhancer or silencer

33
Q

what do enhancers typically activate

A

the promoter nearest to itself

34
Q

what are mediator complexes

A

controls transcription by recruiting either protein-coding RNA or non-coding RNA genes to promote or repress transcription initiation - they adapt easily

35
Q

how do enhancers work

A

by increasing the concentration of activators near the promoter

36
Q

what is p53a

A

a TF

37
Q

what does a cap at the 5’ end of mRNA enable

A

reading by a ribosome

38
Q

what happens during splicing

A

pre-mRNA exon-intron junctions are broken, and exons are joined to create mature mRNA

39
Q

how are 5’ methylated caps formed

A

by adding a G to the terminal base of the transcript via a 5’-5’ link

40
Q

where does the capping process take place

A

during transcription

41
Q

what are the splice site consensus sequences

A

5’ splice site = GU
3’ splice site = AG

42
Q

how are splice junctions read

A

in pairs

43
Q

how many stages does splicing occur in

A

2

44
Q

what are the stages in splicing

A
  • first the 5’ exon is cleaved off
  • the intron is then released as a lariat when it is cleaved at the 3’ splice site, and the left and right exons are then ligated together
45
Q

when can splicing occur

A

during or after transcription

46
Q

what is splicing connected to

A

the mRNA export and stability control

47
Q

what is alternative splicing

A

exons from the same gene are joined in different combinations, leading to different mRNA transcripts

48
Q

what are the different modes of alternative splicing

A
  • intron retention
  • alternative 5’ splice sites
  • alternative 3’ splice sites
  • exon inclusion/skipping
  • mutually exclusive exons
  • combinatorial exon selection
  • alternative promoter/splicing
  • alternative polyadenylation/splicing
49
Q

what are the 3’ ends of mRNAs generated by

A

cleavage and polyadenylation

50
Q

what is the sequence AAUAAA a signal for

A

cleavage to generate a 3’ end of mRNA that is polyadenylated

51
Q

what do poly(A)polymerases do

A

add ~200 A residues to the 3’ end of the RNA

52
Q

where do the specificity factor and endonuclease cleave RNA

A

downstream of AAUAAA

53
Q

what does the poly(A) tail control

A

mRNA stability and influences translation

54
Q

what are siRNAs

A

~21-22 nucleotides long
incorporated into RNA-induced silencing complex (RISC)
involved in gene regulation, transposon control and viral defence

55
Q

what are miRNAs

A

~19-22 nucleotides long
incorportated with argonaute proteins into RNA-induced silencing complex
involved in post-transriptional gene regulation

cell proliferation (12 decks)

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