INSTANT
PASS! 2026/2027
Biology 203 Exam 4 Questions And
Answers Latest Update 2026
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Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor - Answer D) repressor
A lack of which molecule would result in a cell's inability to "turn off"
genes?
A) operon
B) inducer
,INSTANT
PASS! 2026/2027
C) promoter
D) corepressor - Answer D) corepressor
Which of the following, when taken up by a cell, binds to a repressor so
that the repressor no longer binds to the operator?
A) inducer
B) promoter
C) repressor
D) corepressor - Answer A) inducer
Most repressor proteins are allosteric. Which of the following binds
with the repressor to alter its conformation?
A) inducer
B) promoter
C) transcription factor
D) cAMP - Answer A) inducer
A mutation that inactivates a regulatory gene of a repressible operon in
an E. coli cell would result in _____.
A) continuous transcription of the structural gene controlled by that
regulator
,INSTANT
PASS! 2026/2027
B) complete inhibition of transcription of the structural gene controlled
by that regulator
C) irreversible binding of the repressor to the operator
D) continuous translation of the mRNA because of alteration of its
structure - Answer A) continuous transcription of the structural
gene controlled by that regulator
The lactose operon is likely to be transcribed when _____.
A) there is more glucose in the cell than lactose
B) there is glucose but no lactose in the cell
C) the cyclic AMP and lactose levels are both high within the cell
D) the cAMP level is high and the lactose level is low - Answer C) the
cyclic AMP and lactose levels are both high within the cell
Transcription of structural genes in an inducible operon _____.
A) occurs continuously in the cell
B) starts when the pathway's substrate is present
C) starts when the pathway's product is present
D) stops when the pathway's product is present - Answer B) starts
when the pathway's substrate is present
, INSTANT
PASS! 2026/2027
For a repressible operon to be transcribed, which of the following must
occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must
be inactive.
D) RNA polymerase must not occupy the promoter, and the repressor
must be inactive. - Answer C) RNA polymerase must bind to the
promoter, and the repressor must be inactive.
Altering patterns of gene expression in prokaryotes would most likely
serve an organism's survival by _____.
A) organizing gene expression, so that genes are expressed in a given
order
B) allowing each gene to be expressed an equal number of times
C) allowing an organism to adjust to changes in environmental
conditions
D) allowing environmental changes to alter a prokaryote's genome -
Answer C) allowing an organism to adjust to changes in
environmental conditions
In positive control of several sugar-metabolism-related operons, the
catabolite activator protein (CAP) binds to DNA to stimulate
PASS! 2026/2027
Biology 203 Exam 4 Questions And
Answers Latest Update 2026
EMAIL ME FOR MORE INFO :
Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor - Answer D) repressor
A lack of which molecule would result in a cell's inability to "turn off"
genes?
A) operon
B) inducer
,INSTANT
PASS! 2026/2027
C) promoter
D) corepressor - Answer D) corepressor
Which of the following, when taken up by a cell, binds to a repressor so
that the repressor no longer binds to the operator?
A) inducer
B) promoter
C) repressor
D) corepressor - Answer A) inducer
Most repressor proteins are allosteric. Which of the following binds
with the repressor to alter its conformation?
A) inducer
B) promoter
C) transcription factor
D) cAMP - Answer A) inducer
A mutation that inactivates a regulatory gene of a repressible operon in
an E. coli cell would result in _____.
A) continuous transcription of the structural gene controlled by that
regulator
,INSTANT
PASS! 2026/2027
B) complete inhibition of transcription of the structural gene controlled
by that regulator
C) irreversible binding of the repressor to the operator
D) continuous translation of the mRNA because of alteration of its
structure - Answer A) continuous transcription of the structural
gene controlled by that regulator
The lactose operon is likely to be transcribed when _____.
A) there is more glucose in the cell than lactose
B) there is glucose but no lactose in the cell
C) the cyclic AMP and lactose levels are both high within the cell
D) the cAMP level is high and the lactose level is low - Answer C) the
cyclic AMP and lactose levels are both high within the cell
Transcription of structural genes in an inducible operon _____.
A) occurs continuously in the cell
B) starts when the pathway's substrate is present
C) starts when the pathway's product is present
D) stops when the pathway's product is present - Answer B) starts
when the pathway's substrate is present
, INSTANT
PASS! 2026/2027
For a repressible operon to be transcribed, which of the following must
occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must
be inactive.
D) RNA polymerase must not occupy the promoter, and the repressor
must be inactive. - Answer C) RNA polymerase must bind to the
promoter, and the repressor must be inactive.
Altering patterns of gene expression in prokaryotes would most likely
serve an organism's survival by _____.
A) organizing gene expression, so that genes are expressed in a given
order
B) allowing each gene to be expressed an equal number of times
C) allowing an organism to adjust to changes in environmental
conditions
D) allowing environmental changes to alter a prokaryote's genome -
Answer C) allowing an organism to adjust to changes in
environmental conditions
In positive control of several sugar-metabolism-related operons, the
catabolite activator protein (CAP) binds to DNA to stimulate
