Control of Gene Expression

Question 1

list example operons

Answer 1

Lac
Arp
Trp

Question 2

operator

Answer 2

allows RNA Pol to access DNA strand and start replication

Question 3

repressors

Answer 3

regulatory proteins that bind to operator

Question 4

operon senses glucose levels, sugar/carbon source

Answer 4

lac operon

Question 5

gene expression cleaves lac operon to

Answer 5

allolactose (inducer)

interacts with the repressor

Question 6

when inducer is bound to repressor what happens at operator?

Answer 6

it is not bound to operator

you need Cap to promote transcription

Question 7

CAP

Answer 7

catabolite repression/global regulation

Question 8

requirements for transcription on lac operon

Answer 8

CAP active and allolactose bound to operator

Question 9

what happens when: lactose but no glucose

Answer 9

Allolactose is inactive, not bound

CAP is bound to CAP site

transcription occurs

Question 10

what happens when neither lactose or glucose is available

Answer 10

transcription is blocked by repressor

Question 11

what happens when lactose and glucose are available

Answer 11

transcription is inhabited by lack of CAP

Question 12

what happens when lactose is not available but glucose is

Answer 12

Allalactose is bound

CAP is not bound

transcription is inhibited by lac of CAP and presence of repressor

Question 13

CAP requires ___ to bind

Answer 13

no glucose

Question 14

Allalactose requires ___ to bind

Answer 14

no lactose

will not be bound if lactose is present

Question 15

CAP activity is modulated by

Answer 15

cAMP

levels of cAMP are controlled by adenyl cyclase (converts ATP to cAMP) – must have high levels of adenyl cyclase to get lots of cAMP so you must have low glucose

adenyl cyclase active only when little or no glucose is present

Question 16

large quantities/high levels of tryptophan acts as ___

Answer 16

co-repressor of Trp Operon

Question 17

Trp operon is on when

Answer 17

tryptophan is low

Question 18

activity of tryptophan as a corepressor of Trp Operon

Answer 18

binds to repressor protein and blocks transcription (binds operator and blocks RNA Pol)

Question 19

Trp expression is regulated by:

Answer 19

repression (on and can be turned off) and attenuation

Question 20

attenuation

Answer 20

alteration of translation to alternate transcription

formation of termination loop that causes dissociation of Pol thru putting pressure on

Question 21

regulatory protein or Arb protein

Answer 21

AraC

also regulated by global regulation

Question 22

AraC

Answer 22

regulator that does both

activates transcription and turns off transcription

3 binding sites

Question 23

absence of Arb

Answer 23

results in bending of DNA and 2 AraC form a dimer

Question 24

Arb is available

Answer 24

Arb binds

AraC releases

results in dimer of AraC bound to Arb at key site to promote transcription

Question 25

Riboswitches

Answer 25

way to regulate gene expression many systems results in folding of leader sequence to determine if transcription continues or is terminated depends on RNA and ability to form 2' structure

Question 26

Gram - and riboswitch

Answer 26

can either free up shine delgarno so that 16s can bind or not (influences what happens)

Question 27

Riboswitches regulate translation of ___ in gram -

Answer 27

mRNA

Question 28

mechanisms of Riboswitches

Answer 28

binding to metabolite which alters structure OR binding to a ligand to alter

Question 29

which bacteria have OmpC and OmpF

Answer 29

Gram - outer membrane, so they must have outer membrane protein cores

Question 30

OmpF

Answer 30

opening of lager pore | allows more to flow through

Question 31

opening of a smaller pore to allow less diffusion is which of the Omp?

Answer 31

OmpC

Question 32

Regulation of Omp

Answer 32

depending on environment, upregulation/rexpression of 1 and inhibition of expression of other

Question 33

Mechanisms of expression of Omps

Answer 33

micro RNA (OmpF, binds) 2 component systems (sensor kinase -- senses environment -gut or nah- which then causes phosphorylation of response regulator (ompR))

Question 34

OmpR

Answer 34

response regulator (protein 2)

Question 35

EmpZ

Answer 35

sensor kinase of OmpC/OmpF system

Question 36

how do you determine if clockwise or counter clockwise

Answer 36

methylation or ligand binding

Question 37

ligand binding > methylation spinning =

Answer 37

run, so moving counter clockwise

Question 38

methylation >

Answer 38

attractant has already bound, and used up what's there tumble, stimulates clockwise rotation

Question 39

CheA

Answer 39

phosphorylates sensor kinase

Question 40

to continue on a run, not going to spin

Answer 40

CheA is NOT phosphorylated

Question 41

When high [attractant] proteins are:

Answer 41

CheR= methylated CheA= phosphorylated

Question 42

CheR

Answer 42

adds methyl groups

Question 43

CheB

Answer 43

removes methyl groups promotes continuation of run