Chapter 7: Operons & Control of Prokaryotic Transcription

Question 1

activator protein

Answer 1

stimulates transcription (allolactose)

Question 1

ara operon

Answer 1

catabolic, repressible

contains 2 operators, control gene, CAP-binding site (200bp upsteam of promoter)

4 arabinose-metabolizing genes (A-D) and AraC gene

regulated by AraC protein & DNA looping

Question 1

turns operon (switch) off

Answer 1

Repressor

Question 2

cluster of genes containing an operator, promoter, and metabolic enzyme genes

Answer 2

Operon

Question 2

main operator (O₁ @ +11) and 2 auxillary operators (O₂ @ +412 & O₃ @ -82)

Answer 2

3 lac operators

Question 3

inducer in lac operon

produced by B-gal from lactose

Answer 3

allolactase

Question 4

Muller-Hill

Answer 4

performed genetic mutations in each of the 3 (E. coli) lac operators and found they repressed lacZ transcription ~1300-fold

Question 4

single mRNA from >1 gene (i.e. lac genes)

Answer 4

polycistronic message

Question 5

3 enzymes needed to metabolize lactose (by E. coli)

Answer 5

galctoside permease (lacY), B-galactosidase (lacZ), and galactoside transacetylase (lacA)

Question 6

araO₂

Answer 6

250bp upstream of promoter

controls transcription b/c DNA loops out from protein-DNA & protein-protein interactions (prevents RNA polymerase binding promoter)

Question 7

Repressor

Answer 7

turns operon (switch) off

Question 7

AraC

Answer 7

exerts negative control w/ out arabinose, positive control w/ arabinose (binds O₁, O₂, l₁, and l₂ within operator)

also engages in autoregulation, binding O₁ (controls leftward transcription of araC) and inhibiting its own production when araC levels are high

Question 7

attenuation

Answer 7

used in negative control of trp operon

trp leader & attenuator DNA (aka attenuator; between operator and first trp E gene) form inverted repeat (3&4) in RNA (hairpin), stopping translation through ribosome (and possibly RNA polymerase) interferance

blocked by low trp levels (2-3 pairing prevents 3-4 and creates strong ribosome-binding site)

Question 8

galctoside permease (lacY), B-galactosidase (lacZ), and galactoside transacetylase (lacA)

Answer 8

3 enzymes needed to metabolize lactose (by E. coli)

Question 10

3 lac operators

Answer 10

main operator (O₁ @ +11) and 2 auxillary operators (O₂ @ +412 & O₃ @ -82)

Question 10

contacts DNA & CTD of holoenzyme, causing closed promoter complex formation and transcription initiation (when bound to cAMP; independent of allolactose)

Answer 10

CAP (catabolite activator protein)

Question 11

performed genetic mutations in each of the 3 (E. coli) lac operators and found they repressed lacZ transcription ~1300-fold

Answer 11

Muller-Hill

Question 13

Operon

Answer 13

cluster of genes containing an operator, promoter, and metabolic enzyme genes

Question 14

stimulates transcription (allolactose)

Answer 14

activator protein

Question 16

negative control

Answer 16

always on unless something stops it (lac operon)

Question 16

binds operator to prevent RNA polymerase transcription

allosterically regulated w/ inducer (allolactase) binding

Answer 16

lac repressor

Question 18

allolactase

Answer 18

inducer in lac operon

produced by B-gal from lactose

Question 19

exerts negative control w/ out arabinose, positive control w/ arabinose (binds O₁, O₂, l₁, and l₂ within operator)

also engages in autoregulation, binding O₁ (controls leftward transcription of araC) and inhibiting its own production when araC levels are high

Answer 19

AraC

Question 21

cAMP

Answer 21

second messenger derived from ATP (using adenylyl cyclase) sensitiveto low glucose levels

stimulates lac operon with catabolite activator protein (CAP) association by binding activator site containing TGTGA (facilitates RNA polymerase binding to promoter and opens up DNA)

Question 23

polycistronic message

Answer 23

single mRNA from >1 gene (i.e. lac genes)

Question 24

used in negative control of trp operon

trp leader & attenuator DNA (aka attenuator; between operator and first trp E gene) form inverted repeat (3&4) in RNA (hairpin), stopping translation through ribosome (and possibly RNA polymerase) interferance

blocked by low trp levels (2-3 pairing prevents 3-4 and creates strong ribosome-binding site)

Answer 24

attenuation

Question 25

always on unless something stops it (lac operon)

Answer 25

negative control

Question 26

catabolic, repressible

contains 2 operators, control gene, CAP-binding site (200bp upsteam of promoter)

4 arabinose-metabolizing genes (A-D) and AraC gene

regulated by AraC protein & DNA looping

Answer 26

ara operon

Question 27

developed the E. coli lac operon

Answer 27

Francois Jacob & Jacques Monod (1940’s)

Question 28

CAP (catabolite activator protein)

Answer 28

contacts DNA & CTD of holoenzyme, causing closed promoter complex formation and transcription initiation (when bound to cAMP; independent of allolactose)

Question 29

anabolic, repressible

contains 5 genes & operator w/in promoter

Answer 29

trp operon

Question 31

trp operon

Answer 31

anabolic, repressible

contains 5 genes & operator w/in promoter

Question 33

250bp upstream of promoter

controls transcription b/c DNA loops out from protein-DNA & protein-protein interactions (prevents RNA polymerase binding promoter)

Answer 33

araO₂

Question 34

lac repressor

Answer 34

binds operator to prevent RNA polymerase transcription

allosterically regulated w/ inducer (allolactase) binding

Question 35

Francois Jacob & Jacques Monod (1940’s)

Answer 35

developed the E. coli lac operon

Question 36

second messenger derived from ATP (using adenylyl cyclase) sensitiveto low glucose levels

stimulates lac operon with catabolite activator protein (CAP) association by binding activator site containing TGTGA (facilitates RNA polymerase binding to promoter and opens up DNA)

Answer 36

cAMP