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Genetics 97 > ADL Lecture 3: 14.1-3 > Flashcards

ADL Lecture 3: 14.1-3 Flashcards

Regulation of Gene Expression in Prokaryotes

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1
Q

Constitutive transcription

A

state in which a gene is continuously transcribed (in bacteria, some genes need to be Constitutively transcribed in order to perform certain tasks)

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2
Q

regulated transcription

A

condition in which gene expression is controlled at the transcriptional level in response to changing environmental conditions. (controls initiation/amount of transcription) most regulation of gene expression in bacteria is regulated trans.

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3
Q

negative control of gene transcription

A

binding of a repressor protein to reg. DNA to prevent transcription

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4
Q

positive control of gene transcription

A

binding of activator protein to reg. DNA sequence to initiate transcription

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5
Q

Repressor proteins

A
  • exert neg. control of transcription

- can be activated/inactivated via interactions with other compounds

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6
Q

Binding of repressor protein to DNA sequence results in…

A

no transcription

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7
Q

Binding of inducer molecule to repressor protein results in…

A

transcription

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8
Q

binding of repressor-corepressor complex results in…

A

no transcription

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9
Q

with corepressor absent, the repressor protein…

A

does not bind to DNA sequence and allows transcriptions

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10
Q

Activator proteins

A

bind to regulatory DNA sequences and help initiate transcription

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11
Q

Absence of the allosteric effetor compound… (results in what? in relation to activator proteins)

A

prevents activator protein binding and inhibits transcription

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12
Q

Effector binding to activator protein…

A

facilitates RNA polymerase binding at promoters helps initate transcription

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13
Q

Binding of the allosteric inhibitor compound to the activator protein…

A

prevents activtor protein binding/transcription

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14
Q

absence of an inhibitor molecule (in relation to an activator protein)

A

allos binding of activator protein and transcription

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15
Q

What are the two active sites in repressor proteins and what do they do?

A
  1. DNA-binding domain: responsible for finding/binding operator DNA sequence/target regulatory sequences
  2. Allosteric domain: binds molecule or protein-causing change in shape of DNA-binding site
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16
Q

lacl
Function:
Product type:

A
  1. contains two binding sites, one for operator and one for lactose, the inducer (continuously expressed)
  2. repressor protein
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17
Q

lacZ
Function:
product type:

A
  1. Cleaves lactose into 2 monosaccharides (glucose/galactose)
  2. B-galactosidase
18
Q

lacY
function:
product type:

A
  1. facilitates lactose transport across cell membrane

2. permease

19
Q

lacA
function:
product type:

A
  1. protects against harmful by-products of lactose metabolism
  2. transacetylase
20
Q

lacO
function:
product type:

A
  1. binds repressor protein to block transcription of operon genes
  2. operator
21
Q

lacP
function:
product type:

A
  1. binds RNA polymerase

2. promoter

22
Q

operons

A

clusters of genes undergoing coordinated transcriptional regulation by shared regulatory region (common in bacterial genomes-genes participate in same metabolic/biosynthesis pathway)

23
Q

lactose (lac) operon

A

responsible for producing three polypeptides needed for lactose

24
Q

lactose metabolism

A

enzyme B-galactosidase cleaves B-galactoside linkage of disaccharide lactose and yeilds monosaccharides of glucose and galactose

25
Q

Which monosaccaride is the preferred source of energy for E. Coli? and what biochemical pathway is it metabolized by?

A

glucose; glycolsis

26
Q

inducible systems

A

turned on only when an inducer compound is avaiable

27
Q

What sugar can serve as an alternate carbon source?

A

lactose

28
Q

lac+ phenotype vs lac- phenotype

A

lac + able to grow on medium containing lactose as only sugar
lac- unable to grow on a loctose-containing medium

29
Q

allolactose

A

acts as inducer compound; alternate form of lactose

30
Q

Describe the lac operon structure

A
  1. has multipart regulatory region (promoter-binds RNA pol; lacO-binds repressor protein; CAP-cAMP region; all partially overlap)
  2. three structural genes
31
Q

polycistronic mRNA

A

translated to produce three distinct polypeptides

32
Q

Describe (in order) the sequences/sites of the promoter region, regulatory region and the lactose operon region

A

Short: lacl promoter; lacl; CAP site; lacP; lacO; lacZ; lacY; lacA

  1. Promoter region: (within regulatory region) CAP site; lacP; lacO
  2. Regulatory region: same as promoter region except is contains a lacl gene before the CAP site and a lacZ gene after the operator
  3. The lactose operon contains the regulatory region in additoin to the lacY and lacA genes immediately following
33
Q

Lac operon function

A
  1. when lactose is unavailable and glucose is availabe- transcription in inhibited lac repressor protein binds to lacO (negative control)
  2. when lactose is availabe and glucose in unavailabe- transcription is carried out
    (repressor protein inactivated by allolactose binding–prevents binding to lacO- inducer-repressor complex)
34
Q

Is cAMP increase or decreases during glycolysis and what is the result?

A

cAMP is decreased; CAP-cAMP complex cannot form; makes transcription inefficient – called catabolite repression

35
Q

If lacZ and lacY are wild-type/trans-heterozygotes under lactose induction, what doe this tell yoiu?

A

That the two mutations complement one another

36
Q

constitutive mutants

A

transcribed continuously whether or not lactose is availabe

37
Q

lacl+ (wild-type) vs lacl- (repressor mutation- mutation in DNA binding domain)

A

lacl+ : reprossor binds to lacO when inducer is absent/ doesn’t bind to lacO when inducer-repressor complex is formed
lacl- : prevents binding to lacO; produces conotinuous synthesis of lac operon

38
Q

lacO^c (operator constitutive mutation)

A

prevents repressor protein binding; produces continuous synthesis of lac operon

39
Q

lacI^s (super-repressor mutation)

A

repressor protein mutation blocks binding to inducer; preventing formation of complex; mutated protein binds to lacO which inhibts transcription (genes are unresponsive in presence of lactose)

40
Q

what is the result if lacP is mutated?

A

reduced/eliminated transcription

41
Q

Why is the lac operon ON only when glucose is absent and lactose is present?

A

sadf

42
Q

If bacteria were diploids what would be the effect of the different lac mutations as heterozygotes in against a wild-type allele?

A

sdf

Genetics 97 (8 decks)

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