Foundations of Biology Exam 3 Answered

University of Pittsburgh at Greensburg – Foundations of Biology Exam 3


Student Version
Name of Student: Calista Greives. Student ID:……………………………….

Instructor Name: Nayyar Ahmed

Foundations of Bio II Exam 3 - Chapters: 18, 19 & 31 Date: 07/15/2020

Total Points: /75 Time allocation: 1 hour & 10 min
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MULTIPLE CHOICE QUESTIONS:


1) Which of the following molecules is a protein produced by a regulatory gene?
A) Operon.
B) Inducer.
C) Promoter.
D) Repressor.


2) Which of the following molecules helps to "turn off" genes in a cell?
A) Operon.
B) Inducer.
C) Promoter.
D) Corepressor.


3) When taken up by a cell, which of the following molecules binds to a repressor so that
the repressor no longer binds to the operator?
A) Inducer.
B) Promoter.
C) Repressor.
D) Corepressor.


4) Most repressor proteins are allosteric. Which of the following molecules binds with the
repressor to alter its conformation and therefore affect its function?
A) Inducer.
B) Promoter.
C) transcription factor.
D) cAMP.




5) Which of the following conditions is most likely to cause the lactose operon to be
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, University of Pittsburgh at Greensburg – Foundations of Biology Exam 3

transcribed?
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.


6) How does the transcription of structural genes in an inducible operon occur?
A) It occurs continuously in the cell.
B) It starts when the pathway's substrate is present.
C) It starts when the pathway's product is present.
D) It stops when the pathway's product is present.


7) For a repressible operon to be transcribed, which of the following conditions 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.


8) 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.


9) In positive control of several sugar metabolism-related operons, the cAMP receptor
protein (CRP) binds to DNA to stimulate transcription. Which of the following
environmental conditions causes an increase in CRP activity in stimulating transcription?
A) an increase in glucose and an increase in cAMP.
B) a decrease in glucose and an increase in cAMP.
C) an increase in glucose and a decrease in cAMP.
D) a decrease in glucose and a decrease in the repressor.




10) Suppose an experimenter becomes proficient with a technique that allows her to move
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, University of Pittsburgh at Greensburg – Foundations of Biology Exam 3

DNA sequences within a prokaryotic genome. If a researcher moves the promoter for the
lac operon to the region between the beta galactosidase (lacZ) gene and the permease
(lacY) gene, which of the following results would be most likely?
A) The three genes of the lac operon will be expressed normally.
B) RNA polymerase will no longer transcribe permease.
C) The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be
translated.
D) Beta galactosidase will not be produced.


11) Suppose an experimenter becomes proficient with a technique that allows her to move
DNA sequences within a prokaryotic genome. If a researcher moves the operator to the
far end of the operon, past the transacetylase (lacA) gene, which of the following
processes would likely occur when the cell is exposed to lactose?
A) The inducer will no longer bind to the repressor.
B) The repressor will no longer bind to the operator.
C) The operon will never be transcribed.
D) The genes of the lac operon will be transcribed continuously.


12) Suppose an experimenter becomes proficient with a technique that allows her to move
DNA sequences within a prokaryotic genome. If a researcher moves the repressor gene
(lacI), along with its promoter, to a position at some several thousand base pairs away
from its normal position, which of the following results would be expected?
A) The repressor will no longer bind to the operator.
B) The repressor will no longer bind to the inducer.
C) The lac operon will function normally.
D) The lac operon will be expressed continuously.


13) Which of the following results would occur if the repressor of an inducible operon were
mutated so that it could not bind the operator?
A) the irreversible binding of the repressor to the promoter.
B) the reduced transcription of the operon's genes.
C) the continuous transcription of the operon's genes.
D) the overproduction of cAMP receptor protein (CRP).


14) Under what conditions does the trp repressor block transcription of the trp operon?
A) when the repressor binds to the inducer.
B) when the repressor binds to tryptophan.
C) when the repressor is not bound to tryptophan.
D) when the repressor is not bound to the operator.



15) How does extracellular glucose inhibit transcription of the lac operon?
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