BIOL 142 Lecture 31: Exam 3 Review
30 Apr 2018
School
Department
Course
Professor
1.#In#what#way#does#the#insulin#receptor#(IRK)#differ#from#the#EGF#receptor#(EGFR)?#
The#insulin#receptor#is#preformed#prior#to#ligand#binding
Exists#as#a#tetramer
â—‹
When#inactivated,#exists#as#a#tetramer#regardless#of#if#a#signal#is#bound#to#
it#or#not
â—‹
A.
A#tyrosine#kinase#active#site#is#activated.#
B.
Phosphorylation#of#one#half#of#the#receptor#complex#is#catalyzed#by#enzyme#
active#sites#on#the#other#half
C.
ATP#is#required#for#phosphorylation.#
D.
The#insulin#receptor#is#a#cell-surface#receptor.#
E.
Both#cell-surface#enzyme-linked#receptors
Enzymatic#domains#in#the#cell#called#tyrosine#kinase#domain#(not#B#or#E)
•
Activated#by#hydrophilic#signals
•
C#is#a#description#of#trans-auto-phosphorylation#(not#C)
Epidermal#GF#in#inactive#state#exist#as#monomers
â—‹
When#signals#bind,#triggers#dimerization
â—‹
Allows#tyrosine#kinase#domain#of#one#member#of#the#dimer#to#
phosphorylate#and#add#them#to#the#opposite#side#of#the#dimer
â—‹
Two#alpha#units#outside#the#cell# and#two#beta#subunits#that#span#the#
membrane
â—‹
•
Response#of#the#Insulin#Receptor#Tyrosine#Kinase#(IRK)#to#Insulin#binding#
The#Insulin#receptor#is#a#heterotetramer#(2α#and#2β)#composed#of#distinct#α#and#
β#subunits.#How#is#the#receptor#activated?#
The#α#subunit#binds#to#Insulin.#
â—‹
The#β#subunit#transmits#a#signal#from#bound#Insulin#to#the#cytoplasmic#
domain#by#a#conformational#change#in#structure.#
â—‹
The#conformational#change#activates#the#kinase#domain#in#the#cytoplasm.#
â—‹
The#β#subunit#phosphorylates#Tyrosine#residues#(amino#acids)#on#the#
receptor#cytoplasmic#domain#as#well#as#the#downstream#substrate,#Insulin#
Response#Substrate#(IRS)#
â—‹
•
2.#Which#of#the#following#statements#about#evolution#by#natural#selection#is#correct?#
When#individuals#change#in#response#to#challenges#from#the#environment,#their#
altered#traits#are#passed#on#to#offspring.#
A.
Species#are#created#independently#of#each#other#and#do#not#change#over#time.#B.
Populations,#not#individuals,#change#when#natural#selection#occurs.#C.
A#human#is#better#adapted#to#it's#environment#than#a#tapeworm,#thus#humans#
are#correctly#referred#to#as#being#"higher"#organisms.#
D.
In#the#process#of#evolution,#individual#members#do#not#change
The#degree#to#which#individuals#survive#and#produce#viable#offspring#in#turn#
being#able#to#reproduce#is#what#varies
•
Darwin#broke#down#the#process#of#evolution#by#natural#selection#into#four#steps
Individuals#that#make#up#a#population#vary%in#their#traits.1.
Some#of#these#trait#differences#are#heritable,#meaning#they#are#passed#on#to#
offspring
2.
In#each#generation,#many#more#offspring#are#produced#than#can#survive.#Only#
some#individuals#in#the#population#survive#long#enough#to#produce#offspring.#Of#
these,#some#will#produce#more#offspring#than#others.#
3.
Individuals#with#certain#heritable#traits#are#more#likely#to#survive#and#
reproduce.#Natural#selection#occurs#when#individuals#with#certain#traits#produce#
more#offspring#than#do#individuals#without#those#traits.#
4.
These#selected# traits#will#increase#in#frequency#in#the#population#from#one#
generation#to#the#next,#causing#evolution—a#change#in#the#genetic#
characteristics#of#a#population)over#time.#
Individuals#don't#change,#but#the#action#of#the#environment#on#individuals#
can#lead#to#a#change#in#the#frequency#of#particular#alleles# in#a#given#
population#
â—‹
•
Therefore,#evolution#is#the#outcome#of#these#four#steps.•
3.#A#cell#is#found#that#contains#three#Barr#bodies.#This#cell#has:#
three#Y#chromosomesA.
three#X#chromosomesB.
four#Y#chromosomesC.
four#X#chromosomesD.
three#nucleoliE.
If#you#silenced#all#3,#there#would#be#no#expression
One#bar#body#forms#when#an#X#gets#silenced•
You#condense#all#but#one#of#the#X#chromosomes•
Normally#have#one#Barr#body#because#only#one#is#silenced•
So#if#3#were#silenced,#there#would#be#4#chromosomes#so#only#one#is#expressed•
4.#Which#statement#regarding#ubiquitin#is#correct?#Ubiquitin:#
is#a#carbohydrate#group#that#marks#proteins#for#destruction#in#proteasomes.#A.
is#a#polypeptide#that#marks#proteins#for#destruction#in#proteasomes.#B.
is#attached#to#proteins#by#the#RISC#complex.#C.
is#found#in#both#prokaryotes#and#eukaryotesD.
ANSWER:
Have#to#be#tagged#by#ubiquitin#to#go#into#the#proteasome•
RISC#is#the#complex#of#proteins#that#miRNAs#interact#with#to#regulate#life#span#of#
mRNA
Regulates#biomolecule#also,#but#it's#mRNA#and#not#protein
â—‹
•
Only#happens#in#eukaryotes•
5.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#inhibited#by#drug#treatment,#after#probing#a#DNA#microarray#with#
your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
Red#B.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
Treatment:#presence#of#a#drug•
–drug#culture#(control)#-->#GREEN
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(experimental)#-->#RED
-X->#mRNA#(not#expressed) -->#cDNA#-->#red
â—‹
•
Procedure:
Let#cells#grow#and#incubate
â—‹
Extract#mRNA#from#both#batches#of#cells#
â—‹
Use#reverse#transcriptase#to#make#complementary#DNAs#(cDNAs)
â—‹
•
Need#to#distinguish#where#cDNA#came#from#(cells#with#or#without#drug)#so#add#
fluorescent#tags
•
If#a#gene#is#being#inhibited,#and#mRNA#for#that#gene#would#not#be#formed
No#mRNA#made#for#that#gene
â—‹
Are#green#probes#that#bind#to#the#array#for#the#spot#for#that#gene
â—‹
What#lights#up#green#says#what#genes#are#being#turned#down#by#the#drug
â—‹
Looking#for#green#spots#to#know#what#genes#are#expressed#when#we#have#
no#drug#and#what#are#expressed#when#we#have#the#drug
â—‹
•
6.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#enhanced#(increased)#by#drug#treatment,#after#probing#a#DNA#
microarray#with#your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
RedB.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
–drug#culture#(control)#-->#GREEN
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(control)#-->#RED
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##red
â—‹
•
Yellow#is#having#an#equal#amount#of#green#and#red#probes
Yellow#means#there#is#no#effect#with#the#drug
â—‹
Gene#is#expressed#with#the#drug#and#without#the#drug
â—‹
Drug#does#not#change#the#expression#of#that#gene
â—‹
•
7.#What#is#the#effect#upon#the#lac)operon#when#both#glucose#and#lactose#are#absent#
from#E.)coli’s#environment?#
The#catabolite#activator#protein#(CAP)#binding#site#would#be#empty.#The#lac#
repressor#would#bind#to#the#operator.#Infrequent#transcription#results.#
A.
The#cAMP-CAP#complex#would#bind#to#the#operator.#The#lac#repressor#would#
bind#to#the#CAP-binding#site.#Infrequent#transcription#results.#
B.
CAP#would#bind#to#the#CAP-binding#site.#The#lac#repressor#would#be#absent#from#
the#operator.#Frequent#transcription#results.#
C.
cAMP-CAP#complex#would#bind#to#the#CAP#binding#site.#The#lac#repressor#
would#bind#to#the#operator.#Infrequent#transcription#results.#
D.
ANSWER
When#lactose#levels#are#low
Lac#repressor#will#be#able#to#bind#to#the#operator#region#of#the#lac#operon
â—‹
Represses#expression
â—‹
Negative)control
â—‹
•
When#glucose#levels#are#low
cAMP#levels#are#high#when#glucose#is#low
â—‹
cAMP#binds#to#CAP
â—‹
CAP#binds#to#CAP#binding#site#near#the#promoter
â—‹
Positive)control
â—‹
•
8.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#the#
bacterial#colonies#will#turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
Not#told#about#what#carbohydrate#source#is#in#the#media•
9.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#with#
both#lactose#and#glucose#used#as#carbohydrate#sources,#the#bacterial#colonies#will#
turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
High#lactose#causes#removal#of#repressor•
High#glucose
Low#cAMP,#no#promotion#of#expression#from#lac#operon
â—‹
Low#levels#of#beta#galactosidase,#so#not#much#for#X-Gal#to#cut
â—‹
•
When#glucose#is#high#(and#cAMP#levels#are#low),#even#when#lactose#is#available,#the#
lac)operon#fails#to#transcribe#frequently.#
CAP#not#bound#to#cAMP,#does#not#bind#to#the#CAP#binding#site.#•
If#cAMP#levels#are#low,#CAP#is#not#active#and#transcription#is#not)increased.#•
The#amount#of#cAMP#and#the#rate#of#lac)transcription#are#inversely#related#to#
the#concentration#of#glucose.#
•
10.#In#a#repressible#operon,#the#repressor#molecule:#
must#first#be#activated#by#a#corepressor.#A.
can#repress#the#transcription#of#the#operon#on#its#
own.#
B.
is#a#molecule#made#from#the#operon.#C.
binds#to#the#mRNA.#D.
Inducible#and#repressible#systems
In#inducible#systems,#an#inducer#from#the#cell’s#environment#prevents#a#
repressor#from#blocking#transcription#(eg—lac)operon).#
Lac#operon#is#inducible#–need#lactose#to#remove#a#repressor#
â—‹
•
In#repressible#systems,#a#corepressor#produced#by#the#cell#activates#a#repressor,#
enabling#it#to#block#transcription#(eg—trp)operon).#
Need#tryptophan#to#add#the#repressor
â—‹
•
When#tryptophan#(an#e.g.#of#a#corepressor)#is#present,#it#binds#to#a#repressor,#which#
becomes#active.#
The#molecule#that#binds#and#activates#a#repressor#is#called#a#corepressor#and#
may#be#the#end#product#of#the#operon#(as#in#the#case#of#tryptophan).#
Tryptophan#acts#as#corepressor
â—‹
If#you#have#a#lot#of#tryptophan,#don't#need#any#more
â—‹
•
The#activated#repressor#binds#to#the#operator#of#the#trp)operon,#blocking#
production#of#enzymes#for#tryptophan#synthesis.
•
Trp#operon#encodes#everything#needed#for#tryptophan#synthesis•
Repressor#NOT#made#from#same#operon
Independent#of#the#operon#and#always#being#made/expressed
â—‹
•
11.#Which#of#the#following#statements#regarding#the#tryptophan#operon#is#correct?#
The#trp)operon:#
codes#for#proteins#needed#for#tryptophan#synthesis.#A.
codes#for#proteins#needed#to#break#down#
tryptophan.#
B.
is#activated#by#the#presence#of#tryptophan.#C.
is#inducible.#D.
All#of#these#choices#are#correct.#E.
In#the#absence#of#tryptophan,#RNA#polymerase#transcribes#the#trp)operon,#leading#to#
production#of#enzymes#that#synthesize#tryptophan.#
If#synthesis#of#an#enzyme#can#be#turned#off,#it#is#said#to#be#repressible.#•
The#trp%operon#in#E.)coli)is#repressible.#•
See#the#animation#of#the#trp)operon)on#Canvas•
12.#Steroid#hormones#are#lipid0soluble#signal#molecules#that#cross#the#plasma#
membrane.#If#these#molecules#can#enter#all#cells,#why#do#only#specific#cells#respond#to#
their#presence?#
Nontarget#cells#lack#the#intracellular#receptors#that,#when#activated#by#the#
signal#molecule,#can#interact#with#genes#in#the#cell's#nucleus.#
A.
Nontarget#cells#possess#enzymes#that#immediately#degrade#the#molecules#as#
they#enter#the#cell.#
B.
Nontarget#cells#lack#the#inactive#enzymes#that#the#signal#molecules#activate.#C.
In#nontarget#cells#these#signal#molecules#cross#the#membranes#of#the#
endoplasmic#reticulum#and#are#captured#by#vesicles.#
D.
ANSWER
Can#cross#plasma#membrane#of#lots#of#cells,#why#do#only#certain#cells#respond?•
Cell#is#only#going#to#respond#to#a#signal#if#the#cell#has#a#receptor#for#that#signal
Can#cross#a#membrane#that#has#no#receptor#and#no#response#would#be#
generated
â—‹
•
13.#Which#of#the#following#statements#is#false#regarding#the#epidermal#growth#factor#
receptor#(EGFR)?#
Binding#of#epidermal#growth#factor#results#in#dimerization#of#the#receptor.#A.
Dimerization#activates#the#tyrosine#kinase#active#site.#B.
Activation#of#tyrosine#kinase#results#in#phosphorylation#of#
tyrosine#residues#on#the#other#half#of#the#dimer.#
C.
GTP#is#required#for#phosphorylation.#D.
14.#What#type#of#protein#is#Ras?#
A#tyrosine#kinaseA.
A#serine-threonine#kinase#B.
A#small#monomeric#GTPase#switch#protein#C.
A#trimeric#G#protein#switch#D.
An#intracellular#hormone#receptor#E.
Exam%3%Review
Monday,#April#30,#2018
11:25#AM
1.#In#what#way#does#the#insulin#receptor#(IRK)#differ#from#the#EGF#receptor#(EGFR)?#
The#insulin#receptor#is#preformed#prior#to#ligand#binding
Exists#as#a#tetramer
â—‹
When#inactivated,#exists#as#a#tetramer#regardless#of#if#a#signal#is#bound#to#
it#or#not
â—‹
A.
A#tyrosine#kinase#active#site#is#activated.#B.
Phosphorylation#of#one#half#of#the#receptor#complex#is#catalyzed#by#enzyme#
active#sites#on#the#other#half
C.
ATP#is#required#for#phosphorylation.#D.
The#insulin#receptor#is#a#cell-surface#receptor.#E.
Both#cell-surface#enzyme-linked#receptors
Enzymatic#domains#in#the#cell#called#tyrosine#kinase#domain#(not#B#or#E)•
Activated#by#hydrophilic#signals•
C#is#a#description#of#trans-auto-phosphorylation#(not#C)
Epidermal#GF#in#inactive#state#exist#as#monomers
â—‹
When#signals#bind,#triggers#dimerization
â—‹
Allows#tyrosine#kinase#domain#of#one#member#of#the#dimer#to#
phosphorylate#and#add#them#to#the#opposite#side#of#the#dimer
â—‹
Two#alpha#units#outside#the#cell# and#two#beta#subunits#that#span#the#
membrane
â—‹
•
Response#of#the#Insulin#Receptor#Tyrosine#Kinase#(IRK)#to#Insulin#binding#
The#Insulin#receptor#is#a#heterotetramer#(2α#and#2β)#composed#of#distinct#α#and#
β#subunits.#How#is#the#receptor#activated?#
The#α#subunit#binds#to#Insulin.#
â—‹
The#β#subunit#transmits#a#signal#from#bound#Insulin#to#the#cytoplasmic#
domain#by#a#conformational#change#in#structure.#
â—‹
The#conformational#change#activates#the#kinase#domain#in#the#cytoplasm.#
â—‹
The#β#subunit#phosphorylates#Tyrosine#residues#(amino#acids)#on#the#
receptor#cytoplasmic#domain#as#well#as#the#downstream#substrate,#Insulin#
Response#Substrate#(IRS)#
â—‹
•
2.#Which#of#the#following#statements#about#evolution#by#natural#selection#is#correct?#
When#individuals#change#in#response#to#challenges#from#the#environment,#their#
altered#traits#are#passed#on#to#offspring.#
A.
Species#are#created#independently#of#each#other#and#do#not#change#over#time.#
B.
Populations,#not#individuals,#change#when#natural#selection#occurs.#
C.
A#human#is#better#adapted#to#it's#environment#than#a#tapeworm,#thus#humans#
are#correctly#referred#to#as#being#"higher"#organisms.#
D.
In#the#process#of#evolution,#individual#members#do#not#change
The#degree#to#which#individuals#survive#and#produce#viable#offspring#in#turn#
being#able#to#reproduce#is#what#varies
•
Darwin#broke#down#the#process#of#evolution#by#natural#selection#into#four#steps
Individuals#that#make#up#a#population#vary%in#their#traits.
1.
Some#of#these#trait#differences#are#heritable,#meaning#they#are#passed#on#to#
offspring
2.
In#each#generation,#many#more#offspring#are#produced#than#can#survive.#Only#
some#individuals#in#the#population#survive#long#enough#to#produce#offspring.#Of#
these,#some#will#produce#more#offspring#than#others.#
3.
Individuals#with#certain#heritable#traits#are#more#likely#to#survive#and#
reproduce.#Natural#selection#occurs#when#individuals#with#certain#traits#produce#
more#offspring#than#do#individuals#without#those#traits.#
4.
These#selected# traits#will#increase#in#frequency#in#the#population#from#one#
generation#to#the#next,#causing#evolution—a#change#in#the#genetic#
characteristics#of#a#population)over#time.#
Individuals#don't#change,#but#the#action#of#the#environment#on#individuals#
can#lead#to#a#change#in#the#frequency#of#particular#alleles# in#a#given#
population#
â—‹
•
Therefore,#evolution#is#the#outcome#of#these#four#steps.•
3.#A#cell#is#found#that#contains#three#Barr#bodies.#This#cell#has:#
three#Y#chromosomesA.
three#X#chromosomesB.
four#Y#chromosomesC.
four#X#chromosomesD.
three#nucleoliE.
If#you#silenced#all#3,#there#would#be#no#expression
One#bar#body#forms#when#an#X#gets#silenced•
You#condense#all#but#one#of#the#X#chromosomes•
Normally#have#one#Barr#body#because#only#one#is#silenced•
So#if#3#were#silenced,#there#would#be#4#chromosomes#so#only#one#is#expressed•
4.#Which#statement#regarding#ubiquitin#is#correct?#Ubiquitin:#
is#a#carbohydrate#group#that#marks#proteins#for#destruction#in#proteasomes.#A.
is#a#polypeptide#that#marks#proteins#for#destruction#in#proteasomes.#B.
is#attached#to#proteins#by#the#RISC#complex.#C.
is#found#in#both#prokaryotes#and#eukaryotesD.
ANSWER:
Have#to#be#tagged#by#ubiquitin#to#go#into#the#proteasome•
RISC#is#the#complex#of#proteins#that#miRNAs#interact#with#to#regulate#life#span#of#
mRNA
Regulates#biomolecule#also,#but#it's#mRNA#and#not#protein
â—‹
•
Only#happens#in#eukaryotes•
5.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#inhibited#by#drug#treatment,#after#probing#a#DNA#microarray#with#
your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
Red#B.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
Treatment:#presence#of#a#drug•
–drug#culture#(control)#-->#GREEN
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(experimental)#-->#RED
-X->#mRNA#(not#expressed) -->#cDNA#-->#red
â—‹
•
Procedure:
Let#cells#grow#and#incubate
â—‹
Extract#mRNA#from#both#batches#of#cells#
â—‹
Use#reverse#transcriptase#to#make#complementary#DNAs#(cDNAs)
â—‹
•
Need#to#distinguish#where#cDNA#came#from#(cells#with#or#without#drug)#so#add#
fluorescent#tags
•
If#a#gene#is#being#inhibited,#and#mRNA#for#that#gene#would#not#be#formed
No#mRNA#made#for#that#gene
â—‹
Are#green#probes#that#bind#to#the#array#for#the#spot#for#that#gene
â—‹
What#lights#up#green#says#what#genes#are#being#turned#down#by#the#drug
â—‹
Looking#for#green#spots#to#know#what#genes#are#expressed#when#we#have#
no#drug#and#what#are#expressed#when#we#have#the#drug
â—‹
•
6.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#enhanced#(increased)#by#drug#treatment,#after#probing#a#DNA#
microarray#with#your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
RedB.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
–drug#culture#(control)#-->#GREEN
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(control)#-->#RED
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##red
â—‹
•
Yellow#is#having#an#equal#amount#of#green#and#red#probes
Yellow#means#there#is#no#effect#with#the#drug
â—‹
Gene#is#expressed#with#the#drug#and#without#the#drug
â—‹
Drug#does#not#change#the#expression#of#that#gene
â—‹
•
7.#What#is#the#effect#upon#the#lac)operon#when#both#glucose#and#lactose#are#absent#
from#E.)coli’s#environment?#
The#catabolite#activator#protein#(CAP)#binding#site#would#be#empty.#The#lac#
repressor#would#bind#to#the#operator.#Infrequent#transcription#results.#
A.
The#cAMP-CAP#complex#would#bind#to#the#operator.#The#lac#repressor#would#
bind#to#the#CAP-binding#site.#Infrequent#transcription#results.#
B.
CAP#would#bind#to#the#CAP-binding#site.#The#lac#repressor#would#be#absent#from#
the#operator.#Frequent#transcription#results.#
C.
cAMP-CAP#complex#would#bind#to#the#CAP#binding#site.#The#lac#repressor#
would#bind#to#the#operator.#Infrequent#transcription#results.#
D.
ANSWER
When#lactose#levels#are#low
Lac#repressor#will#be#able#to#bind#to#the#operator#region#of#the#lac#operon
â—‹
Represses#expression
â—‹
Negative)control
â—‹
•
When#glucose#levels#are#low
cAMP#levels#are#high#when#glucose#is#low
â—‹
cAMP#binds#to#CAP
â—‹
CAP#binds#to#CAP#binding#site#near#the#promoter
â—‹
Positive)control
â—‹
•
8.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#the#
bacterial#colonies#will#turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
Not#told#about#what#carbohydrate#source#is#in#the#media•
9.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#with#
both#lactose#and#glucose#used#as#carbohydrate#sources,#the#bacterial#colonies#will#
turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
High#lactose#causes#removal#of#repressor•
High#glucose
Low#cAMP,#no#promotion#of#expression#from#lac#operon
â—‹
Low#levels#of#beta#galactosidase,#so#not#much#for#X-Gal#to#cut
â—‹
•
When#glucose#is#high#(and#cAMP#levels#are#low),#even#when#lactose#is#available,#the#
lac)operon#fails#to#transcribe#frequently.#
CAP#not#bound#to#cAMP,#does#not#bind#to#the#CAP#binding#site.#•
If#cAMP#levels#are#low,#CAP#is#not#active#and#transcription#is#not)increased.#•
The#amount#of#cAMP#and#the#rate#of#lac)transcription#are#inversely#related#to#
the#concentration#of#glucose.#
•
10.#In#a#repressible#operon,#the#repressor#molecule:#
must#first#be#activated#by#a#corepressor.#A.
can#repress#the#transcription#of#the#operon#on#its#
own.#
B.
is#a#molecule#made#from#the#operon.#C.
binds#to#the#mRNA.#D.
Inducible#and#repressible#systems
In#inducible#systems,#an#inducer#from#the#cell’s#environment#prevents#a#
repressor#from#blocking#transcription#(eg—lac)operon).#
Lac#operon#is#inducible#–need#lactose#to#remove#a#repressor#
â—‹
•
In#repressible#systems,#a#corepressor#produced#by#the#cell#activates#a#repressor,#
enabling#it#to#block#transcription#(eg—trp)operon).#
Need#tryptophan#to#add#the#repressor
â—‹
•
When#tryptophan#(an#e.g.#of#a#corepressor)#is#present,#it#binds#to#a#repressor,#which#
becomes#active.#
The#molecule#that#binds#and#activates#a#repressor#is#called#a#corepressor#and#
may#be#the#end#product#of#the#operon#(as#in#the#case#of#tryptophan).#
Tryptophan#acts#as#corepressor
â—‹
If#you#have#a#lot#of#tryptophan,#don't#need#any#more
â—‹
•
The#activated#repressor#binds#to#the#operator#of#the#trp)operon,#blocking#
production#of#enzymes#for#tryptophan#synthesis.
•
Trp#operon#encodes#everything#needed#for#tryptophan#synthesis•
Repressor#NOT#made#from#same#operon
Independent#of#the#operon#and#always#being#made/expressed
â—‹
•
11.#Which#of#the#following#statements#regarding#the#tryptophan#operon#is#correct?#
The#trp)operon:#
codes#for#proteins#needed#for#tryptophan#synthesis.#A.
codes#for#proteins#needed#to#break#down#
tryptophan.#
B.
is#activated#by#the#presence#of#tryptophan.#C.
is#inducible.#D.
All#of#these#choices#are#correct.#E.
In#the#absence#of#tryptophan,#RNA#polymerase#transcribes#the#trp)operon,#leading#to#
production#of#enzymes#that#synthesize#tryptophan.#
If#synthesis#of#an#enzyme#can#be#turned#off,#it#is#said#to#be#repressible.#•
The#trp%operon#in#E.)coli)is#repressible.#•
See#the#animation#of#the#trp)operon)on#Canvas•
12.#Steroid#hormones#are#lipid0soluble#signal#molecules#that#cross#the#plasma#
membrane.#If#these#molecules#can#enter#all#cells,#why#do#only#specific#cells#respond#to#
their#presence?#
Nontarget#cells#lack#the#intracellular#receptors#that,#when#activated#by#the#
signal#molecule,#can#interact#with#genes#in#the#cell's#nucleus.#
A.
Nontarget#cells#possess#enzymes#that#immediately#degrade#the#molecules#as#
they#enter#the#cell.#
B.
Nontarget#cells#lack#the#inactive#enzymes#that#the#signal#molecules#activate.#C.
In#nontarget#cells#these#signal#molecules#cross#the#membranes#of#the#
endoplasmic#reticulum#and#are#captured#by#vesicles.#
D.
ANSWER
Can#cross#plasma#membrane#of#lots#of#cells,#why#do#only#certain#cells#respond?•
Cell#is#only#going#to#respond#to#a#signal#if#the#cell#has#a#receptor#for#that#signal
Can#cross#a#membrane#that#has#no#receptor#and#no#response#would#be#
generated
â—‹
•
13.#Which#of#the#following#statements#is#false#regarding#the#epidermal#growth#factor#
receptor#(EGFR)?#
Binding#of#epidermal#growth#factor#results#in#dimerization#of#the#receptor.#A.
Dimerization#activates#the#tyrosine#kinase#active#site.#B.
Activation#of#tyrosine#kinase#results#in#phosphorylation#of#
tyrosine#residues#on#the#other#half#of#the#dimer.#
C.
GTP#is#required#for#phosphorylation.#D.
14.#What#type#of#protein#is#Ras?#
A#tyrosine#kinaseA.
A#serine-threonine#kinase#B.
A#small#monomeric#GTPase#switch#protein#C.
A#trimeric#G#protein#switch#D.
An#intracellular#hormone#receptor#E.
Exam%3%Review
Monday,#April#30,#2018 11:25#AM
1.#In#what#way#does#the#insulin#receptor#(IRK)#differ#from#the#EGF#receptor#(EGFR)?#
The#insulin#receptor#is#preformed#prior#to#ligand#binding
Exists#as#a#tetramer
â—‹
When#inactivated,#exists#as#a#tetramer#regardless#of#if#a#signal#is#bound#to#
it#or#not
â—‹
A.
A#tyrosine#kinase#active#site#is#activated.#B.
Phosphorylation#of#one#half#of#the#receptor#complex#is#catalyzed#by#enzyme#
active#sites#on#the#other#half
C.
ATP#is#required#for#phosphorylation.#D.
The#insulin#receptor#is#a#cell-surface#receptor.#E.
Both#cell-surface#enzyme-linked#receptors
Enzymatic#domains#in#the#cell#called#tyrosine#kinase#domain#(not#B#or#E)•
Activated#by#hydrophilic#signals•
C#is#a#description#of#trans-auto-phosphorylation#(not#C)
Epidermal#GF#in#inactive#state#exist#as#monomers
â—‹
When#signals#bind,#triggers#dimerization
â—‹
Allows#tyrosine#kinase#domain#of#one#member#of#the#dimer#to#
phosphorylate#and#add#them#to#the#opposite#side#of#the#dimer
â—‹
Two#alpha#units#outside#the#cell# and#two#beta#subunits#that#span#the#
membrane
â—‹
•
Response#of#the#Insulin#Receptor#Tyrosine#Kinase#(IRK)#to#Insulin#binding#
The#Insulin#receptor#is#a#heterotetramer#(2α#and#2β)#composed#of#distinct#α#and#
β#subunits.#How#is#the#receptor#activated?#
The#α#subunit#binds#to#Insulin.#
â—‹
The#β#subunit#transmits#a#signal#from#bound#Insulin#to#the#cytoplasmic#
domain#by#a#conformational#change#in#structure.#
â—‹
The#conformational#change#activates#the#kinase#domain#in#the#cytoplasm.#
â—‹
The#β#subunit#phosphorylates#Tyrosine#residues#(amino#acids)#on#the#
receptor#cytoplasmic#domain#as#well#as#the#downstream#substrate,#Insulin#
Response#Substrate#(IRS)#
â—‹
•
2.#Which#of#the#following#statements#about#evolution#by#natural#selection#is#correct?#
When#individuals#change#in#response#to#challenges#from#the#environment,#their#
altered#traits#are#passed#on#to#offspring.#
A.
Species#are#created#independently#of#each#other#and#do#not#change#over#time.#B.
Populations,#not#individuals,#change#when#natural#selection#occurs.#C.
A#human#is#better#adapted#to#it's#environment#than#a#tapeworm,#thus#humans#
are#correctly#referred#to#as#being#"higher"#organisms.#
D.
In#the#process#of#evolution,#individual#members#do#not#change
The#degree#to#which#individuals#survive#and#produce#viable#offspring#in#turn#
being#able#to#reproduce#is#what#varies
•
Darwin#broke#down#the#process#of#evolution#by#natural#selection#into#four#steps
Individuals#that#make#up#a#population#vary%in#their#traits.1.
Some#of#these#trait#differences#are#heritable,#meaning#they#are#passed#on#to#
offspring
2.
In#each#generation,#many#more#offspring#are#produced#than#can#survive.#Only#
some#individuals#in#the#population#survive#long#enough#to#produce#offspring.#Of#
these,#some#will#produce#more#offspring#than#others.#
3.
Individuals#with#certain#heritable#traits#are#more#likely#to#survive#and#
reproduce.#Natural#selection#occurs#when#individuals#with#certain#traits#produce#
more#offspring#than#do#individuals#without#those#traits.#
4.
These#selected# traits#will#increase#in#frequency#in#the#population#from#one#
generation#to#the#next,#causing#evolution—a#change#in#the#genetic#
characteristics#of#a#population)over#time.#
Individuals#don't#change,#but#the#action#of#the#environment#on#individuals#
can#lead#to#a#change#in#the#frequency#of#particular#alleles# in#a#given#
population#
â—‹
•
Therefore,#evolution#is#the#outcome#of#these#four#steps.
•
3.#A#cell#is#found#that#contains#three#Barr#bodies.#This#cell#has:#
three#Y#chromosomes
A.
three#X#chromosomes
B.
four#Y#chromosomes
C.
four#X#chromosomes
D.
three#nucleoli
E.
If#you#silenced#all#3,#there#would#be#no#expression
One#bar#body#forms#when#an#X#gets#silenced
•
You#condense#all#but#one#of#the#X#chromosomes
•
Normally#have#one#Barr#body#because#only#one#is#silenced
•
So#if#3#were#silenced,#there#would#be#4#chromosomes#so#only#one#is#expressed
•
4.#Which#statement#regarding#ubiquitin#is#correct?#Ubiquitin:#
is#a#carbohydrate#group#that#marks#proteins#for#destruction#in#proteasomes.#
A.
is#a#polypeptide#that#marks#proteins#for#destruction#in#proteasomes.#
B.
is#attached#to#proteins#by#the#RISC#complex.#
C.
is#found#in#both#prokaryotes#and#eukaryotes
D.
ANSWER:
Have#to#be#tagged#by#ubiquitin#to#go#into#the#proteasome
•
RISC#is#the#complex#of#proteins#that#miRNAs#interact#with#to#regulate#life#span#of#
mRNA
Regulates#biomolecule#also,#but#it's#mRNA#and#not#protein
â—‹
•
Only#happens#in#eukaryotes
•
5.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#inhibited#by#drug#treatment,#after#probing#a#DNA#microarray#with#
your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
Red#B.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
Treatment:#presence#of#a#drug•
–drug#culture#(control)#-->#GREEN
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(experimental)#-->#RED
-X->#mRNA#(not#expressed) -->#cDNA#-->#red
â—‹
•
Procedure:
Let#cells#grow#and#incubate
â—‹
Extract#mRNA#from#both#batches#of#cells#
â—‹
Use#reverse#transcriptase#to#make#complementary#DNAs#(cDNAs)
â—‹
•
Need#to#distinguish#where#cDNA#came#from#(cells#with#or#without#drug)#so#add#
fluorescent#tags
•
If#a#gene#is#being#inhibited,#and#mRNA#for#that#gene#would#not#be#formed
No#mRNA#made#for#that#gene
â—‹
Are#green#probes#that#bind#to#the#array#for#the#spot#for#that#gene
â—‹
What#lights#up#green#says#what#genes#are#being#turned#down#by#the#drug
â—‹
Looking#for#green#spots#to#know#what#genes#are#expressed#when#we#have#
no#drug#and#what#are#expressed#when#we#have#the#drug
â—‹
•
6.#Imagine#you#are#using#a#DNA#microarray#to#test#the#effect#of#a#drug#treatment#on#
gene#expression.#To#perform#this#experiment,#you#administer#the#drug#to#cells#grown#
in#culture#for#several#days.#As#a#negative#control,#you#culture#cells#under#similar#
conditions#without#the#drug.#
You#generate#cDNA#from#cells#under#each#condition#and#label#the#cDNA#with#
fluorescent#tags#for#use#in#a#microarray—cDNA#from#drug-treated#cells#was#labeled#in#
red#and#cDNA#from#negative#control#cells# labeled#in#green.#To#search#for#genes#whose#
expression#was#enhanced#(increased)#by#drug#treatment,#after#probing#a#DNA#
microarray#with#your#labeled#cDNA,#you#would#search#for:#
High-levels#of#expression.#A.
RedB.
Green#C.
Yellow#D.
None#of#these#answers#are#correct.#E.
ANSWER
–drug#culture#(control)#-->#GREEN
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##green
â—‹
•
+#drug#culture#(control)#-->#RED
Increase#mRNA,#more#cDNA#made
â—‹
-->#mRNA#-->#cDNA#-->##red
â—‹
•
Yellow#is#having#an#equal#amount#of#green#and#red#probes
Yellow#means#there#is#no#effect#with#the#drug
â—‹
Gene#is#expressed#with#the#drug#and#without#the#drug
â—‹
Drug#does#not#change#the#expression#of#that#gene
â—‹
•
7.#What#is#the#effect#upon#the#lac)operon#when#both#glucose#and#lactose#are#absent#
from#E.)coli’s#environment?#
The#catabolite#activator#protein#(CAP)#binding#site#would#be#empty.#The#lac#
repressor#would#bind#to#the#operator.#Infrequent#transcription#results.#
A.
The#cAMP-CAP#complex#would#bind#to#the#operator.#The#lac#repressor#would#
bind#to#the#CAP-binding#site.#Infrequent#transcription#results.#
B.
CAP#would#bind#to#the#CAP-binding#site.#The#lac#repressor#would#be#absent#from#
the#operator.#Frequent#transcription#results.#
C.
cAMP-CAP#complex#would#bind#to#the#CAP#binding#site.#The#lac#repressor#
would#bind#to#the#operator.#Infrequent#transcription#results.#
D.
ANSWER
When#lactose#levels#are#low
Lac#repressor#will#be#able#to#bind#to#the#operator#region#of#the#lac#operon
â—‹
Represses#expression
â—‹
Negative)control
â—‹
•
When#glucose#levels#are#low
cAMP#levels#are#high#when#glucose#is#low
â—‹
cAMP#binds#to#CAP
â—‹
CAP#binds#to#CAP#binding#site#near#the#promoter
â—‹
Positive)control
â—‹
•
8.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#the#
bacterial#colonies#will#turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
Not#told#about#what#carbohydrate#source#is#in#the#media•
9.#When#wild-type)(normal)#E.)coli)is#grown#on#agar#plates#coated#with#X-Gal,#with#
both#lactose#and#glucose#used#as#carbohydrate#sources,#the#bacterial#colonies#will#
turn:#
blue#A.
white#B.
yellow#C.
orange#D.
there#is#not#enough#information#to#answer#this#question#E.
ANSWER
High#lactose#causes#removal#of#repressor•
High#glucose
Low#cAMP,#no#promotion#of#expression#from#lac#operon
â—‹
Low#levels#of#beta#galactosidase,#so#not#much#for#X-Gal#to#cut
â—‹
•
When#glucose#is#high#(and#cAMP#levels#are#low),#even#when#lactose#is#available,#the#
lac)operon#fails#to#transcribe#frequently.#
CAP#not#bound#to#cAMP,#does#not#bind#to#the#CAP#binding#site.#•
If#cAMP#levels#are#low,#CAP#is#not#active#and#transcription#is#not)increased.#•
The#amount#of#cAMP#and#the#rate#of#lac)transcription#are#inversely#related#to#
the#concentration#of#glucose.#
•
10.#In#a#repressible#operon,#the#repressor#molecule:#
must#first#be#activated#by#a#corepressor.#A.
can#repress#the#transcription#of#the#operon#on#its#
own.#
B.
is#a#molecule#made#from#the#operon.#C.
binds#to#the#mRNA.#D.
Inducible#and#repressible#systems
In#inducible#systems,#an#inducer#from#the#cell’s#environment#prevents#a#
repressor#from#blocking#transcription#(eg—lac)operon).#
Lac#operon#is#inducible#–need#lactose#to#remove#a#repressor#
â—‹
•
In#repressible#systems,#a#corepressor#produced#by#the#cell#activates#a#repressor,#
enabling#it#to#block#transcription#(eg—trp)operon).#
Need#tryptophan#to#add#the#repressor
â—‹
•
When#tryptophan#(an#e.g.#of#a#corepressor)#is#present,#it#binds#to#a#repressor,#which#
becomes#active.#
The#molecule#that#binds#and#activates#a#repressor#is#called#a#corepressor#and#
may#be#the#end#product#of#the#operon#(as#in#the#case#of#tryptophan).#
Tryptophan#acts#as#corepressor
â—‹
If#you#have#a#lot#of#tryptophan,#don't#need#any#more
â—‹
•
The#activated#repressor#binds#to#the#operator#of#the#trp)operon,#blocking#
production#of#enzymes#for#tryptophan#synthesis.
•
Trp#operon#encodes#everything#needed#for#tryptophan#synthesis•
Repressor#NOT#made#from#same#operon
Independent#of#the#operon#and#always#being#made/expressed
â—‹
•
11.#Which#of#the#following#statements#regarding#the#tryptophan#operon#is#correct?#
The#trp)operon:#
codes#for#proteins#needed#for#tryptophan#synthesis.#A.
codes#for#proteins#needed#to#break#down#
tryptophan.#
B.
is#activated#by#the#presence#of#tryptophan.#C.
is#inducible.#D.
All#of#these#choices#are#correct.#E.
In#the#absence#of#tryptophan,#RNA#polymerase#transcribes#the#trp)operon,#leading#to#
production#of#enzymes#that#synthesize#tryptophan.#
If#synthesis#of#an#enzyme#can#be#turned#off,#it#is#said#to#be#repressible.#•
The#trp%operon#in#E.)coli)is#repressible.#•
See#the#animation#of#the#trp)operon)on#Canvas•
12.#Steroid#hormones#are#lipid0soluble#signal#molecules#that#cross#the#plasma#
membrane.#If#these#molecules#can#enter#all#cells,#why#do#only#specific#cells#respond#to#
their#presence?#
Nontarget#cells#lack#the#intracellular#receptors#that,#when#activated#by#the#
signal#molecule,#can#interact#with#genes#in#the#cell's#nucleus.#
A.
Nontarget#cells#possess#enzymes#that#immediately#degrade#the#molecules#as#
they#enter#the#cell.#
B.
Nontarget#cells#lack#the#inactive#enzymes#that#the#signal#molecules#activate.#C.
In#nontarget#cells#these#signal#molecules#cross#the#membranes#of#the#
endoplasmic#reticulum#and#are#captured#by#vesicles.#
D.
ANSWER
Can#cross#plasma#membrane#of#lots#of#cells,#why#do#only#certain#cells#respond?•
Cell#is#only#going#to#respond#to#a#signal#if#the#cell#has#a#receptor#for#that#signal
Can#cross#a#membrane#that#has#no#receptor#and#no#response#would#be#
generated
â—‹
•
13.#Which#of#the#following#statements#is#false#regarding#the#epidermal#growth#factor#
receptor#(EGFR)?#
Binding#of#epidermal#growth#factor#results#in#dimerization#of#the#receptor.#A.
Dimerization#activates#the#tyrosine#kinase#active#site.#B.
Activation#of#tyrosine#kinase#results#in#phosphorylation#of#
tyrosine#residues#on#the#other#half#of#the#dimer.#
C.
GTP#is#required#for#phosphorylation.#D.
14.#What#type#of#protein#is#Ras?#
A#tyrosine#kinaseA.
A#serine-threonine#kinase#B.
A#small#monomeric#GTPase#switch#protein#C.
A#trimeric#G#protein#switch#D.
An#intracellular#hormone#receptor#E.
Exam%3%Review
Monday,#April#30,#2018 11:25#AM
Document Summary
The insulin receptor is preformed prior to ligand binding. When inactivated, exists as a tetramer regardless of if a signal is bound to it or not. Phosphorylation of one half of the receptor complex is catalyzed by enzyme active sites on the other half. Enzymatic domains in the cell called tyrosine kinase domain (not b or e) C is a description of trans-auto-phosphorylation (not c) Epidermal gf in inactive state exist as monomers. Allows tyrosine kinase domain of one member of the dimer to phosphorylate and add them to the opposite side of the dimer. Two alpha units outside the cell and two beta subunits that span the membrane. Response of the insulin receptor tyrosine kinase (irk) to insulin binding. The insulin receptor is a heterotetramer (2 and 2 ) composed of distinct and. The subunit transmits a signal from bound insulin to the cytoplasmic domain by a conformational change in structure.
