Brainscape's Knowledge GenomeTM

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


See full index

MOLBIO OFFSEM MIDTERM > OPERONS: FINE CONTROL OF BACTERIAL TRANSCRIPT > Flashcards

OPERONS: FINE CONTROL OF BACTERIAL TRANSCRIPT Flashcards

1
Q

__________ - first operon discovered which became the prime example
for operon concept

A

Lac Operon

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

contains three (3) coding genes for E. coli protein to permit to use
the sugar lactose

  1. _____________ - transports the lactose into cells
  2. _______________ - cuts lactose into galactose and glucose
  3. ________________ - unclear function in lactose
    metabolism
A

Galactoside permease (lacY)
B - galactosidase (lacZ)
Galactoside transacetylase (lacA)

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

they are transcribed to produce one messenger RNA known as
____________ - comes from a single promoter.

each ________ in the mRNA has its own ribosome binding site so each cistron – can be translated by separate ribosomes that bind independently of each other.

A

polycistronic message ; cistron

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

E. coli cells growing on a medium containing sugars _____ and _____ – cells exhaust the glucose and stop growing

A

glucose and lactose

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

o _______ resumes - after an hour
o ______ - cells have been turning on the lac operon and beginning to accumulate the enzymes they need to metabolize lactose
* _______ - latin word auxilium meaning help
* Bacteria need an enzyme to transport the lactose into the cells named _____________
o Cells - need an enzyme to break the lactose down into 2 component sugars: _________ & ________

A

growth ; During lag ; Diauxic ; Galactoside permease ; Galactose & glucose

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

(CONTROL OF LAC OPERON)

  • like “brake” of car; needed to
    released to be able to move
  • ________ - a protein called as lac
    repressor which keeps the
    operon turned off as long as
    lactose is absent
A

Negative Control ; Brake

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

(CONTROL OF LAC OPERON)

like accelerator pedal

  • ________ - additional postive
    factor; responds to low glucose
    levels by stimulating transcription of
    the lac operon
  • ______ - keep the
    concentration of the activator low,
    so transcription of the operon
    cannot be stimulated
  • Advantage: keeps the operon
    neearly turned off when level of
    glucose is high
A

Positive Control ; Activator ; High glucose levels

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

(NEGATIVE CONTROL OF LAC OPERON)

implies that operon is turned on unless lac repressor intervenes to stop it.

A

Negative control

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

(NEGATIVE CONTROL OF LAC OPERON)

_____________ - lac repressor; turns off the lac operon

o When the repressor binds to the operator or as long as there’s no lactose available, the operon is __________
o Repressor bound to operator – prevents ____________ from binding to the promoter and transcribing the operon

A

Off regulation ; repressed ; RNA polymerase

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

(NEGATIVE CONTROL OF LAC OPERON)

_______ - product of a regulatory gene
- tetramer of 4 identical polypeptide; binds to the operator on the right of promoter

A

lacl gene

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

(NEGATIVE CONTROL OF LAC OPERON)

___________ - an repressor; binds to one molecule to the protein changes the shape of a remote site on
the protein and alters its interaction with a second molecule

A

Allosteric protein

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

(NEGATIVE CONTROL OF LAC OPERON)

Greek: ____ = other + ______ = shape

A

allos ; stereos

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

(NEGATIVE CONTROL OF LAC OPERON)

_______ - first molecule; binds to the repressor causing protein to change to a conformation that favors
dissociation from operator

  • an ____________; alternative form of lactose
A

Inducer ; Allolactose

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

(NEGATIVE CONTROL OF LAC OPERON)

NATURE OF INDUCER
* Inducer of ________ - binds the repressor
* Inducer of ________ - Alternative form of lactose
* When ____________ cleaves lactose to galactose plus glucose, it rearranges a
small fraction of the lactose to allolactose

A

lac operon ; Allolactose ; Beta - galactosidase

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

(DISCOVERY OF THE OPERON)

  • 1940s-1950s; studies the metabolism of lactose by E. coli
  • 3 enzyme activities or genes were induced together by galactosides
  • __________ - needed no induction, genes are active all the time
A

FRANCOIS JACOB AND JACQUES MONOD ; Constitutive mutants

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

(DISCOVERY OF THE OPERON)

studying the inducibility of lactose metabolism in E. coli

A

MONOD, 1940

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

(DISCOVERY OF THE OPERON)

important feature of lactose metabolism

A

BETA-GALACTOSIDASE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

(DISCOVERY OF THE OPERON)

used an anti-beta-galactosidase antibody to detect beta-galactosidase protein

A

MONOD & MELVIN COHN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

(DISCOVERY OF THE OPERON)

  • found that could make beta-galactosidase but still could not grow on lactose
  • ____________ = added radioactive galactoside to wild type and mutant bacteria
  • ___________ - did accumulate the galactoside
A

Monod & co-workers ; Wild type cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

(DISCOVERY OF THE OPERON)

created merodiploids or partial diploid bacteria which carries the both wild type (inducible) and constitutive alleles

A

ARTHUR PARDEE, JACOB AND MONOD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

(DISCOVERY OF THE OPERON)

__________ produces a repressor protein that can diffuse throughout the nucleus

__________ = bind to both operators in ameriploid as it can act on loci on both DNA molecules (Latin: trans = across)

_______ - controls only the operon on the same DNA (known as cis-acting gene)

A

REPRESSOR GENE ; Trans-acting ; Operator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

(REPRESSOR-OPERON INTERACTION)

______________ - succeeded in partially purifying the lac repressor; used a mutant e. coli strain with a repressor mutation (lact) which cause the repressor to bind IPTG (isopropylthiogalactoside)

A

Walter Gilbert and Benno Muller-Hill

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

(REPRESSOR-OPERON INTERACTION)

___________ - used repressor purified or nitrocellulose filter-binding assay and demonstrated that lac repressor binds to lac operator.

showed DNA containing the constitutive mutant operator ________ required a higher concentration of repressor to achieve full binding than did the wild-type operator.

A

Melvin Cohn and his colleagues ; (lacO^c)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

(REPRESSOR-OPERON INTERACTION)

This experiment showed that a genetically defined constitutive lac operator has ______ than normal affinity for the lac repressor, demonstrating that the sites defined genetically and biochemically as the operator are one and the same.

A

lower

25
Q

(THE MECHANISM OF REPRESSION)

____________ does not block access by
RNA polymerase to the lac promoter

A

Repressor

26
Q

(THE MECHANISM OF REPRESSION)

________________ - showed that Polymerase and repressor can bind together to the lac
promoter

A

Susan Straney and Donald Crothers

27
Q

(THE MECHANISM OF REPRESSION)

_______________ - performed kinetic studies in vitro which results to _______________ - is in equilibrium with a free polymerase and promoter

A

Thomas Record and colleagues ; Polymerase- promoter complex

28
Q

(THE MECHANISM OF REPRESSION)

_____________: required for optimum
repression

A

lac Operators

29
Q

(THE MECHANISM OF REPRESSION)

____________ - lies adjacent to promoter;
produces only a modest amount of repression

A

Major lac operator

30
Q

(THE MECHANISM OF REPRESSION)

2 auxiliary lac operators:

A

one upstream & one downstream

31
Q

(POSITIVE CONTROL OF THE LAC OPERON)

Positive control of the lac operon by a substance - sensing a lack of glucose that reponds by activating the ________

A

lac promoter

32
Q

(POSITIVE CONTROL OF THE LAC OPERON)

concentration of a nucleotide (_______ or _____) - rises as concentration of glucose drops

A

cyclic-AMP or cAMP

33
Q

(POSITIVE CONTROL OF THE LAC OPERON)

______________ - showed that crude cell-free extract of E. coli would make B-galactosidase if it is supplied with cAMP

A

Geoffrey Zubay and coworkers

34
Q

(CATABOLITE ACTIVATOR PROTEIN)

cAMP added to _____ - overcome the catabolite repression of lac operon

A

E. coli

35
Q

(CATABOLITE ACTIVATOR PROTEIN)

__________ - leads to activation of lac gene even with the presence of glucose

A

Addition of cAMP

36
Q

(CATABOLITE ACTIVATOR PROTEIN)

2 parts of positive controller of the lac operon:

A
  1. cAMP
  2. Protein factor such as:
    CAP or Catabolite Activator Protein
    CRP or Cyclic-AMP Receptor Protein
    crp - gene encoding this protein
37
Q

(SIMULATION OF LAC OPERON)

CAP - cAMP complex - positively controls the activity of Beta- galactosidase

o _____ - binds cAMP tightly
o _______ - not bind cAMP tightly prepared
o Compare activity and production of __________ using both complexes
o Low activity with mutant CAP – cAMP

A

CAP ; Mutant CAP ; Beta - galactosidase

38
Q

(MECHANISM OF CAP ACTION)

  • ___________ - binds to the lac promoter
  • Mutant whose lac gene is not stimulated by complex - had the mutation in the lac promoter
  • ____________ - showed that the activator-binding site lies just upstream of the promoter
  • _________________ - helps RNA polymerase form an open promoter
A

CAP-cAMP complex ; Mapping the DNA ; Binding CAP and cAMP to the activation site

39
Q

(RECRUITMENT)

  1. Formation of the _____________
  2. Conversion of the closed promoter complex to the ______________
A

closed promoter complex ; open promoter complex

40
Q

(RECRUITMENT)

_______________ summarized these two steps through this equation:

R = RNA polymerase
P = Promoter
RPc = closed promoter complex
RPo = open promoter complex

A

Willian McClure and his colleagues

41
Q

(RECRUITMENT)

__________________ - determined that CAP-cAMP bends its target DNA by
about 100 degress when it binds.

A

Thomaz Steitz and colleagues

42
Q

(RECRUITMENT)

_______________ - using electrophoresis observed the DNA bend in the crystallography studies

A

Hen-Ming Wu and Donald Crothers

43
Q

(THE ARA OPERON)

____________ - codes for enzymes required to metabolize the sugar arabinose , another catabolite-
repressible operon

A

ara operon of E. coli

44
Q

(THE ARA OPERON)

  • Two ara operators exists: _____ & ______
  • ______ - regulated transcription of control gene of ara01
  • _____ is located far upstream of the promoter it controls (PBAD) between position 265 & 294
  • __________ - about 200 bp upstream yet can still stimulate transcription
  • _________- another system of negative regulation
A

ara01 & ara02 ; araC ; ara02 ; CAP-binding site ; AraC protein

45
Q

(THE ARA OPERON)

___________ - controls transcription from a promoter 250 downstream

A

araO2 operator

46
Q

_____________________ found that if they inserted DNA fragments containing an integral number of double-helical turns (multiples of 10.5 bp) between the operator and the promoter, the operator still functioned. However, if the inserts contained a nonintegral number of helical turns (e.g., 5 or 15 bp), the
operator did not function

A

Robert Lobell and Robert Schleif

47
Q

(ARA CONTROL PROTEIN)

______ - act as both positive and negative regulator

A

araC

48
Q

(ARA CONTROL PROTEIN)

3 BINDING site:
1. ______ - far upstream site
2. ______ - located between -106 & -144
3. aral is 2 half sites: _____ - between -56 & -78 and ______- -35 to -51 (each half site can bind to one monomer of AraC

A

ara02 ; ara01 ; aral1 ; aral2

49
Q

(ARA CBAD OPERON)

___________ - also known as araCBAD operon for its 4 genes:

  • Three gene: _____, ____ and ___ - encodes the arabinose metabolizing enzymes
  • transcribes rightward from the promoter ________
  • Other gene, araC which encodes the control protein AraC and transcribed leftward from the araPc promoter
A

ara operon ; asaB, A, and D ; araPBAD

50
Q

(AUTOREGULATION OF ARA C)

allows ______ to regulate its own synthesis

_________ - protein who controls its own synthesis

A

AraC ; autoregulation

51
Q

(THE TRP OPERON)

___________ - genes for enzymes that the bacterium needed to mke the amino acid tryptophan

A

E. coli trp operon

52
Q

(THE TRP OPERON)

______ - codes for anabolic enzymes; exhibits an extra level of control known as attenuation (not seen in lac operon)

  • subject to negative control by repressor when tryptophan levels are elevated
A

trp operon

53
Q

(THE TRP OPERON)

__________ - typically turned off by high level of the substance produces

A

Anabolic enzyme

54
Q

(TRYPTOPHAN’S ROLE IN NEGATIVE
CONTROL OF THE TRP OPERON)

  • ______ - code for the polypeptides
    in the enzymes of tryptophan synthesis
  • ________ - lies wholly within the trp
    promoter
  • ___________________ - is the
    signal to turn off the operon
  • ______________ - helps the trp repressor bind to its operator.
A

Five genes ; trp operator ; High tryptophan concentration ; Presence of tryptophan

55
Q

(NEGATIVE CONTROL OF TRP OPERON)

______________ - no trp repressor exists, just the inactive protein (aporepressor)

If ___________ binds to tryptophan - changes conformation with high affinity
for trp operator

Combine aporepressor and tryptophan - to form the _________

__________ - is a corepressor

A

Without tryptophan ; aporepressor ; trp repressor ; Tryptophan

56
Q

(MECHANISM OF ATTENUATION)

_____________ - imposes an extra level of control on an operon

Operates by causing premature termination of the operon’s transcript when
product is abundant

Presence of ______________ - the RNA polymerase reads
through the attenuator so the structural genes are transcribed

Presence of ______________ - attenuator causes premature termination oftranscription

A

Attenuation ; low tryptophan concentration ; high tryptophan concentration

57
Q

(DEFEATING ATTENUATION)

  • ___________ - operates in the E. coli trp operon as lon as tryptophan is plentiful
  • If amino acid supply is low - ribosomes stall at the tandem tryptophan codons in
    the trp leader
  • _________ - being synthesized as stalling occurs, stalled ribosome will influence the
    way RNA folds
    o Prevents formation of hairpin
    o This is part of the transcription termination signal which causes attenuation
A

Attenuation ; trp leader

58
Q

(RIBOSWITCHES)

_____________ - can act directly on the 5’ UTRs of mRNAs to control their
expression

_____________ - capable of altering their structures to control gene
expression in response to ligand binding called riboswitches.

A

Small molecules ; Regions of 5’ - UTRs

59
Q

(RIBOSWITCHES ACTION)

__________ - region that binds to the ligand

An expression platform is another module in the riboswitch which can be:
o terminator
o Ribosome - binding site
o Another RNA element that affects gene expression

Operates by depressing gene expression
o some work at the transcriptional level
o Others can function at the translational level

A

Aptamer

MOLBIO OFFSEM MIDTERM (9 decks)

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