Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CBG PANT Replication, transcription and translation > CBG Lecture 5: Regulation of transcription > Flashcards

CBG Lecture 5: Regulation of transcription Flashcards

1
Q

what is transcription mainly controlled by

A

cis-acting DNA elements

trans-acting DNA elements`

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how can gene expression in prokaryotes be modified

A

by an interplay between transcription and translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is attenuation

A

an interplay between transcription and translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are cis-acting DNA elements?

A

regulate the DNA close to them by binding gene regulatory proteins
eg. promoter/operator/enhancer
sequences that have to be physically next to eachother to work are cis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

give some examples of cis acting DNA elements

A

promoter
operators
enhancers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are trans-acting DNA elements?

A

must be expressed a gene-regulatory protein to act ad can be relatively far away, even on different chromosomes eg. regulator DNA sequence
examples of trans-acting DNA sequence: Transcription factors, repressors, inducers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

give some examples of trans-acting DNA elements?

A

transcription factors
repressors
inducers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are transcription factors

A

DNA binding roteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

give some examples of the main types of transcription factors and their structures

A

TATA binding protein (TBP) - beta scaffold (unusual for TF)
activator protein 1 (AP1) leucine zipper - generally binds in the major groove
CAP -catabolite activator protein (helix-turn-helix)
Early growth response protein 1 (EGR-1) -> Zinc fingers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is a TBP -give main structure

A

TATA binding protein

beta scaffold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is an AP-1 -give main structure

A

activator protein transcription factor

leucine zipper-generally binds in the major groove and straddles the DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is CAP-give main strucutre

A

transcription factor: catabolite activator protein: helix-turn-helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is EGR-1-give main strucutre

A

early growth response pritein 1 - zinc fingers - have histidine/cysteine residues. fingers poke into major groove

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why does there need to be transcriptional regulation

A

so only express the proteins that are needed, as all cells have the same genome, but different genes expressed in different cells
different condns of same cell = different proteins needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what names do DNA sequences bound by TFs go by

A

low level sequences
OR
high level assemblies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are low level sequences?

A

response element = DNA sequence recognised by protein

eg. in bac: Pribnow box (E.coli) in euk: TATA,CAAT,BRE box ->assembled with large units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are high level assemblies?

A

DNA sequences bound by promoter =RNAP binding
for bac: operator
euk: enhancer, silencer, insulator

18
Q

what 2 things do trans regulatory elements need, to work

A

through interaction between
1)a transcribed and translated TF derived from the trans-regulatory element AND a DNA regulatory element thats adjacent to the regulated gene

19
Q

what control is the trp operon under

A

negative repressible control

20
Q

what is the trp operon regulated by

A

repressor protein

attenuation

21
Q

what is the trp operon composed of

A

trpR gene which synthesizes repressor protein
P:Promoter region where RNAP binds
O-operato region where effector binds (either a repressor or inducer) then structural gene regions trpA to L)
the structural genes encode the enzymes for trp synthesis

22
Q

what does repressible control mean

A

transcription is ON unless an effector is added

23
Q

what does negative control (of an operon) mean

A

transcription is turned OFF by binding to regulatory protein

24
Q

what are operons

A

they are how orikaryotes regulate gene sequences

25
Q

what happens to a prokaryote when concentration of tryptophan is high

A
  1. repressor binds to co-repressor (trp) and becomes able to bind DNA
  2. repressor/corepressor complex blocks transcription by binding operator
  3. no tryptophan structural genes transcribed
26
Q

what happens to a prokaryote when concentration of tryptophan is low

A

turns the trp operon ON
not enough typ available for TrpR to be in DNA-binding form
No TrpR/trp blocking the operator so RNAP can transcribe operon

27
Q

what is autologous repression

give an example of this

A

repression by an element
transcribed within the regulated gene

in the lac operon, lacI represses its own transcription

28
Q

besides repressors, how else is the trp operon controlled

A

by attenuation

29
Q

why does attenuation not happen in eukaryotes

A

because you need interplay between transcription and translation without compartmentalisation using membranes (membranes present in EUKS)

30
Q

overall, what does attenuation do to trp operon

A

can prevent expression of trp biosynthesis genes when trp levels in cell are high

31
Q

how does attenuation work at high tRNAtrp concentration

A

ribosome reads through 1 easily and shields 2, 3&4 form a transcription terminator hairpin

32
Q

how does attenuation work at low tRNAtrp concentration

A

ribosome stalls in 1 waiting for tRNAtrp;
2 binds 3
3&4 cant form transcription terminator hairpin

33
Q

what happens when a 3&4 stem loop is present in trpL mRNa
when a 2&3?

A

it acts with the attenuator (uracil rich sequence) to form a terminator for transcription at end of trpL gene
when a 2&3 stem loop forms, attenuator doesnt form and transcription proceeds to trpE

34
Q

what determines whether ribosomal stalling will happen in mRNA

A

two adjacent trp codons being present in ribosome

35
Q

what are eukaryotic genes controlled by?

give flow chart of control

A

numerous enhancers

enhancer -> mediator -> basal TFs + RNAP (from a long looped distance)

36
Q

what sequence does the lac operon work by

A

tran acting sequence

37
Q

what genes are involved in the lac operon

A

lacI - codes repressor protein
CBS - CAP binding site (catabolite activator protein binding site)
Promoter
Operator
structural genes: lacZ - beta galactosidase
lac Y - lactose permease
lac A - importer protein

38
Q

how does the lac operon work

A

under negative inducible control
repressor is inactivated by binding inducer - lactose
repressor blocks transcription by binding operator

39
Q

what happens when E.coli has high concentrations of glucose and low [lactose]

A

lacI transcribed and translated
repressor blocks transcription by binding operator
RNAP cant bind therefore no structural genes transcribed

40
Q

what happens when E.coli has low [glc] and high [lac]

A

lacI transcribed and translated
repressor blocking transcription by binding operator is INACTIVATED by binding allolactose inducer
no lacI blocking operator so RNAP can transcribe operon

41
Q

what two ways is lac operon controlledq

A

positive control by CAP

negative inducible

42
Q

how is lac operon under positive control

A

by CAP
low [glc] -> high [cAMP] -> CAP/cAMP able to bind CBS(CAP binding site)
transcription is turned ON when regulatory protein (activator is CAP) binds to DNA and actively recruits RNAP

CBG PANT Replication, transcription and translation (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions