Bs161 chapter 15| Questions with 100%
Solutions/Verified Answers
A mutation that disrupts the repressor binding site in the lac operon in an E. Coli cell
would result in ___
A.) inhibition of transcription of the lac operon compared to wild type cells
B.)binding of the repressor to the operator regardless of lactose levels
C.) increased transcription of the lac operon compared to wild type cells - ANSWER
C.) Assuming this is the only form of regulation
Predict which conditions could result in the lac operon being repressed.
A.) Glucose is the only food source
B.) Lactose is the only food source
C.) glucose and lactose are both present as food Sources - ANSWER A.) definitely
, B.) no
C.) maybe, depends on levels
Each of a group of bacterial cells has the mutation described below. Which of these
severely reduce the ability of the cell to metabolize lactose?
A.) A framshift mutation early in the lacZ gene. This gene encodes B-galactosidase, a
key enzyme made by the operon
B.) A point mutation in the lac repressor gene so the repressor cannot bind the inducer
C.) A point mutation in lac repressor gene so the repressor cannot bind to the operator -
ANSWER AB
Which condition will result in maximum expression of the lac operon?
A.) High glucose anf high lactose
B.) High glucose and low lactose
C.) low glucose and high lactose
D.) low glucose and low lactose - ANSWER C.) cAMP is bound to CAP which binds the DNA
activating the operon. allolactose is bound to the lac repressor keeping it off the DNA so
the operon is not repressed
How does the presence of lactose impact the lac repressor protein and transcription of the
lac operon.
A.) The presence of lactose increases the affinity of the protein for the operator and
decreases transcription of the operon
B.) The presence of lactose decreases the affinity of the protein for the operator and decreases
transcription of the operon
C.The presence of lactose increases the affinity of the protein for the operator and
increase transcription of the operon
D.) The presence of lactose decrease the affinity of the protein for the operator and
increase transcription of the operon - ANSWER D.)
Solutions/Verified Answers
A mutation that disrupts the repressor binding site in the lac operon in an E. Coli cell
would result in ___
A.) inhibition of transcription of the lac operon compared to wild type cells
B.)binding of the repressor to the operator regardless of lactose levels
C.) increased transcription of the lac operon compared to wild type cells - ANSWER
C.) Assuming this is the only form of regulation
Predict which conditions could result in the lac operon being repressed.
A.) Glucose is the only food source
B.) Lactose is the only food source
C.) glucose and lactose are both present as food Sources - ANSWER A.) definitely
, B.) no
C.) maybe, depends on levels
Each of a group of bacterial cells has the mutation described below. Which of these
severely reduce the ability of the cell to metabolize lactose?
A.) A framshift mutation early in the lacZ gene. This gene encodes B-galactosidase, a
key enzyme made by the operon
B.) A point mutation in the lac repressor gene so the repressor cannot bind the inducer
C.) A point mutation in lac repressor gene so the repressor cannot bind to the operator -
ANSWER AB
Which condition will result in maximum expression of the lac operon?
A.) High glucose anf high lactose
B.) High glucose and low lactose
C.) low glucose and high lactose
D.) low glucose and low lactose - ANSWER C.) cAMP is bound to CAP which binds the DNA
activating the operon. allolactose is bound to the lac repressor keeping it off the DNA so
the operon is not repressed
How does the presence of lactose impact the lac repressor protein and transcription of the
lac operon.
A.) The presence of lactose increases the affinity of the protein for the operator and
decreases transcription of the operon
B.) The presence of lactose decreases the affinity of the protein for the operator and decreases
transcription of the operon
C.The presence of lactose increases the affinity of the protein for the operator and
increase transcription of the operon
D.) The presence of lactose decrease the affinity of the protein for the operator and
increase transcription of the operon - ANSWER D.)
