In the _______ of lactose, the lac _______ binds to the lac _______ site.
answer
absence; repressor; operator
question
Which of the following statements describes the process regulated by the lac operon?
answer
Buildup of a small molecule induces expression of the enzymes that metabolize the small molecule
question
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?
answer
i
question
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.
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.
question
What is the function of the operator region of the trp operon?
answer
Provides a site for RNA polymerase to bind
question
Under what conditions does the trp repressor become active?
answer
When it binds to tryptophan
question
How does a repressible system such as the trp operon compare to an inducible system such as the lac operon?
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.
question
A student constructed the table as a study guide. He summarized activities of the various components of the trp operon under low and high tryptophan conditions. Evaluate the accuracy of the information shown.
answer
The repressor gene is expressed at the same level under high and low tryptophan levels.
question
What is a TATA box, where is it located, and what is its function?
Which of the following statements regarding RNA polymerase II, the enzyme that synthesizes mRNA in eukaryotic cells, is true?
answer
RNA polymerase II requires other transcription factors in order to bind to a promoter site.
question
In which order do these steps occur just before expression of a gene in a eukaryotic cell?
answer
C → A → D → B
question
A student claims that transcription factors, regulators, and activators only allow eukaryotic cells to turn on genes when they are needed, but do not help to shut down genes when the genes are not needed. Evaluate the accuracy of the student's statement.
answer
The statement is incorrect because transcription factors, regulators, and activators help shut down gene expression by their absence.
Haven't found what you need?
Search for quizzes and test answers now
Quizzes.studymoose.com uses cookies. By continuing you agree to our cookie policy
