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13 biochemistry > L9 - transcription > Flashcards

L9 - transcription Flashcards

1
Q

differences between DNA and RNA

A
  1. DNA double stranded RNA single stranded
  2. DNA has a H instead of OH on 2 carbon
  3. RNA replaces T with U
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2
Q

what type of RNA leaves nucleus to be translated

A

mRNA

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3
Q

what is mRNA

A

copied from DNA in nucleus (transcription)

encodes protein

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4
Q

what is rRNA

A

structural and enzymatic component of ribosome

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5
Q

what is tRNA

A

delivers AAs to ribosome

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6
Q

what type of polymerase is involved in transcription and translation?

A

RNA pol

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7
Q

define transcription

A

production of mRNA from DNA

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8
Q

what are the 3 steps of transcription (in prokaryotes)

A

initiation
elongation
termination

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9
Q

what are the promoter sequences in prokaryotes and what position are they?

A
  1. pribnow box (-10)

2. -35

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10
Q

what are the functions of the promoter recognition sequences

A

align RNA pol to the transcription start site (via sigma factor)

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11
Q

what do promoter recognition sequences often consist of and why?

A

T and A sequence

easier to separate

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12
Q

function of sigma factor

A

recognises the -35 ad -10 promoter and binds them

then recruits the RNA pol in correct space

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13
Q

why is sigma factor needed

A

RNA pol isnt specific so can bind to any region of DNA, sigma factor directs it to the transcription start site

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14
Q

what unwinds the DNA during transcription?

A

RNA pol

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15
Q

describe initiation

A

binding of sigma factor and RNA pol

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16
Q

describe process of elongation

A
  1. RNA pol unwinds DNA as it moves
  2. RNA pol complimentary base pairs NTPs to template strand
  3. sigma factor dissociates after first few nucleotides
17
Q

what provides energy for elongation process of transcription

A

PPi hydrolysis

18
Q

describe process of rho independent termination

A
  1. mRNA transcript G-C rich stem loop sequence
  2. reduces binding of mRNA to DNA and ‘pulls’ it away
  3. after is a A-U rich sequence (easier to pull apart)
19
Q

describe process of rho dependant termination

A
  1. rho protein follows behind DNA pol unwinding the newly synthesised RNA from the DNA strand
  2. DNA pol pauses at certain sequences (eg G-C rich harder to unwind)
  3. rho can catch up to DNA pol and terminate transcription
20
Q

what are the differences between prokaryote transcription and eukaryote transcription

A
  1. eukaryotic has 3 RNA pols
21
Q

what does RNA pol 1 in E synthesise

A

rRNA

22
Q

describe structure of RNA pol 2

A

contains a C terminal domain tail

23
Q

what does RNA pol 2 in E synthesise

A

mRNA and snRNA

24
Q

what does RNA pol 3 in E synthesise

A

5s RNA and tRNA

25
Q

what is pre-mRNA/ hnRNA

A

the mRNA as soon as it has been transcribed

prior to processing

26
Q

what is the function of the CTD tail of DNA pol 2

A

co-transcriptional processing of pre-mRNA by :

  1. capping
  2. polyadenylation
  3. splicing
27
Q

describe process of capping

A

7 methyl guanosine cap formed at 5’ end of mRNA (looks like upside down nucleotide triphosphate)

28
Q

function of capping

A

protects end from degradation
roles in export from nucleus
roles in translation

29
Q

describe process of polyadenylation

A

enzyme adds multiple As to 3’ end of mRNA

not encoded in DNA

30
Q

function of polyadenylation

A

protects end from degradation
roles in export from nucleus
roles in translation

31
Q

are exons or introns expressed

A

EXons

EXpressed

32
Q

what is splicing

A

removal of introns by splicosome

33
Q

what is alternative splicing

A

the process of splicing different combinations of exons as well as introns to give variation in protein products

34
Q

describe the sections of transcribed RNA

A

Tscription start–5’UTR–protein coding region–3’ UTR

13 biochemistry (16 decks)

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