Exam 2: Gene Regulation in E. coli

Question 1

what does it mean when genes are “expressed”

Answer 1

they are transcribed and make their product (RNA or protein)

Question 2

are most genes being transcribed all the time?

Answer 2

no, they have to be turned on or off

output also has to be adjusted up or down

Question 3

RNA polymerase

Answer 3

makes RNA from a DNA template

works with other proteins

Question 4

all promoters bind to…

Answer 4

RNA polymerase

Question 5

stronger promotor binding raises…

Answer 5

transcription rate

Question 6

how to determine promoter strength

Answer 6

depends on how strongly they bind to RNA polymerase

Question 7

holoenzyme

Answer 7

transcription complex of RNA polymerase and different components for different transcription units

Question 8

transcription factor

Answer 8

proteins interacting with the promotor

produce precise and specific transcription control

Question 9

many proteins can influence the …

Answer 9

holoenzyme

Question 10

operon

Answer 10

transcription unit with multiple ORFs

make mRNA that code for multiple proteins

eukaryotes have a few, prokaryotes have many

Question 11

lac. operon normal state of E. coli

Answer 11

no lactose, no transcription, no resources wasted

3 ORFs

Question 12

lac operon transcription controls

Answer 12

repressor, unbinds when lactose present (good)

CAP protein must be bound to promotor, and cAMP must be bound to CAP for this to happen

if glucose present there is low cAMP (bad)

Question 13

cAMP

Answer 13

cyclic AMP

adenosine monophosphate

Question 14

glucose and cAMP

Answer 14

concentrations inversely related

high glucose, low cAMP

low glucose, high cAMP

Question 15

CAP

Answer 15

catabolite activator protein

system keeps variety of other substrate-specific operons turned off if glucose is around

Question 16

why does CAP work

Answer 16

high glucose = low cAMP

other things that need cAMP won’t be transcribed if glucose is high

therefore, glucose is the primary focus for E. coli

Question 17

the lac operon is an …. operon

Answer 17

inducible

Question 18

inducible enzymes

Answer 18

found in breakdown rxns

induced by substrates

Question 19

trp operon normal state in E. coli

Answer 19

continual transcription

Question 20

trp operon transcription controls

Answer 20

repressor binds if tryptophan binds to the repressor

prevents excess tryptophan production if it is present in high concentration

Question 21

the trp operon is an … operon

Answer 21

repressible

Question 22

repressible enzymes

Answer 22

found in synthesizing reactions

repressed by end products

Question 23

are the molecule-to-molecule binding interactions in these mechanisms reversible?

Answer 23

yes

they depend on affinity and concentration

Question 24

do transcription factors regulate the transcription of other transcription factors?

Answer 24

yes