BSC2010 Ch.11 Study Exam Questions
Correctly Answered.
In the _____ of lactose, the lac ____ binds to the lac _____ site - CORRECT ANSWER absence; repressor;
operator
Refer to the figure below. A mutant E. coli cell expresses z, y, and a genes at the same levels in the
presence and absence of lactose. These levels correspond to those observed in wild-type E. coli cells in
the presence of lactose. Which region of the DNA shown in the figure could contain the mutation? -
CORRECT ANSWER i
A student claims that the lac operon is an example of a mechanism that an organism uses to conserve
energy. Evaluate the validity of the student's claim. - CORRECT ANSWER The claim is valid because the
lac operon allows a bacterial cell to shut down a metabolic pathway if it is not immediately needed.
Which of the following statements describes the process regulated by the lac operon? - CORRECT
ANSWER Buildup of a small molecule induces expression of the enzymes that metabolize the small
molecule.
Under what conditions does the trp repressor become active? - CORRECT ANSWER When it binds to the
tryptophan
Refer to the table below. A student constructed the table as a study guide. He summarized the activities
of the various components of the trp operon under low and high tryptophan conditions. Evaluate the
accuracy of the information shown. - CORRECT ANSWER The repressor gene is expressed at the same
level under high and low tryptophan levels.
What is the function of the operator region of the trp operon? - CORRECT ANSWER Provides a site for
the repressor to bind
How does a repressible system such as the trp operon compare to an inducible system such as the lac
operon? - CORRECT ANSWER The repressible system involves repression of gene expression in response
to a signal; the inducible system involves activation of gene expression in response to a signal
Correctly Answered.
In the _____ of lactose, the lac ____ binds to the lac _____ site - CORRECT ANSWER absence; repressor;
operator
Refer to the figure below. A mutant E. coli cell expresses z, y, and a genes at the same levels in the
presence and absence of lactose. These levels correspond to those observed in wild-type E. coli cells in
the presence of lactose. Which region of the DNA shown in the figure could contain the mutation? -
CORRECT ANSWER i
A student claims that the lac operon is an example of a mechanism that an organism uses to conserve
energy. Evaluate the validity of the student's claim. - CORRECT ANSWER The claim is valid because the
lac operon allows a bacterial cell to shut down a metabolic pathway if it is not immediately needed.
Which of the following statements describes the process regulated by the lac operon? - CORRECT
ANSWER Buildup of a small molecule induces expression of the enzymes that metabolize the small
molecule.
Under what conditions does the trp repressor become active? - CORRECT ANSWER When it binds to the
tryptophan
Refer to the table below. A student constructed the table as a study guide. He summarized the activities
of the various components of the trp operon under low and high tryptophan conditions. Evaluate the
accuracy of the information shown. - CORRECT ANSWER The repressor gene is expressed at the same
level under high and low tryptophan levels.
What is the function of the operator region of the trp operon? - CORRECT ANSWER Provides a site for
the repressor to bind
How does a repressible system such as the trp operon compare to an inducible system such as the lac
operon? - CORRECT ANSWER The repressible system involves repression of gene expression in response
to a signal; the inducible system involves activation of gene expression in response to a signal
