Exp 3 Flashcards
what is an operon
it is a group of genes that are involved in a given function and are regulated by a single promoter
for genes under an operon, how are they transcribed
they are regulated together and are transcribed into a single mRNA transcript that is translated into different protein products
what does an operon consist of
more than one gene
a single promoter
regulatory binding sites
in a lac operon what is the role of regulatory binding sites
they are regions in the DNA where regulatory proteins bind and influence RNA polymerase
where are operons found? in what organism
they are found in prokaryotes only
why are operons not found in eukaryotes
eukaryotic genes carry their own individual promoters and are regulated independently
what is the lac operon
this operon contains genes that are involved in lactose metabolism
what is the purpose of lactose metabolism
it allows lactose to be used as an energy source to derive glucose when glucose is absent
why is the lac operon not always active
cells prefer to use all available glucose and only use lactose when nevessaru
what is beta-galactosidase for?
it is an enzyme that cleaves the disaccharide lactose into glucose and galactose which can be further converted into glucose
yield = 2 glucose molecules
what is the cap site and operator
these are the regulatory binding sites
what is the role of the cap site
it is where the CAP binding protein binds in the absence of glucose
what is the role of the operator
it is where the repressor comes OFF in the presence of lactose
what is the bond between galactose and glucose in lactose
a beta bond
what is the purpose of beta bond cleavage
to produce glucose molecules
what is the car brakes and accelerator analogy with the lac operon
the car can only go when the brakes are let off (the supressor) and when the gas pedal is on (the CAP binds)
when will transcription occur in the lac operon
when the CAP binds in the absence of glucose
when the Suppressor releases in the presence of lactose
do the CAP and operator have any affect on eachother
NO they are regulated independently
what is the purpose of sucrose in this experiment
the lac operon is specific to lactose only
it will not produce an enzyme that cleaves sucrose
if the glucose is present and lactose is not, what are the states of the activator (CAP) and repressor?
CAP is off
Repressor is on
if the glucose and lactose are present, what are the states of the activator (CAP) and repressor?
CAP is off
repressor is off
if no glucose or lactose is present, what are the states of the activator (CAP) and repressor?
CAP is on
repressor is on
if no glucose is present but lactose is , what are the states of the activator (CAP) and repressor?
CAP is on
Repressor is off
For the media containing glucose, do we expect high cell growth? what about activation of the Lac Operon and enzyme expression?
high cell growth, no activation
For the media containing sucrose, do we expect high cell growth? what about activation of the Lac Operon and enzyme expression?
no cell growth, no activation
For the media containing lactose, do we expect high cell growth? what about activation of the Lac Operon and enzyme expression?
high cell growth, activation
For the media containing water do we expect high cell growth? what about activation of the Lac Operon and enzyme expression?
no cell growth, no activation
what is the role of ONPG
it has a similar bond to lactose and will be cleaved to form ONP which has a yellow color that can be measured to analyze enzyme activity
why cant we use regular catastrophic reagents
they will denature the proteins
why do we use toulene
it pokes holes in the cells and allows the beta-galactosidase to leak out
what is measured by a spectrophotometer
the amount of light absorbed, it allows us to measure the amount of ONP and cell density
