MCB 450 EXAM 2 CURRENT VERSION 2025-2026
EXAM QUESTIONS AND ACCURATE VERIFIED
ANSWERS/100%PASS/GRADED A+
The major interaction stabilizing the double helical structure of DNA is:
A. hydrogen bonds between bases on the two strands
B. covalent bonds that crosslink the two strands
C. van der Waals interactions between the stacked bases of the double
helix
D. the favorable charge-charge interactions between the two strands
E. hydrogen bonding between the backbone components of the two
strands
-Answer-A. hydrogen bonds between bases on the two strands
In regards to the lac operon in the presence of lactose, will the genes be
transcribed in large amounts?
A. yes; the lactose sugars remove the repressor and the genes will be
transcribed rigorously
B. yes; the lactose sugars bind transcription factors that turn on
transcription
C. no; the lactose sugars do not remove the repressor and the genes will
not be transcribed
D. no; the lac operon does not utilize lactose sugars in its regulatory
mechanism
E. maybe; it depends on the concentration of glucose
-Answer-E. maybe; it depends on the concentration of glucose
In eukaryotes, DNA is present in a chromatin structure. Chromatin is
made up of:
A. DNA that is highly compacted by compartmentalization in a series of
vesicles
B. DNA that is highly compacted by interaction with itself
C. DNA that is tightly associated with the inner face of the nuclear
membrane
,D. DNA that is highly compacted by supercoiling
E. DNA that is highly ordered by wrapping around histones
-Answer-E. DNA that is highly ordered by wrapping around histones
What is the typical location of a promoter in a gene?
A. upstream of the coding region of a gene
B. in the 3' UTR (untranslated region)
C. in the middle of the coding region of a gene
D. downstream of the coding region of a gene
-Answer-A. upstream of the coding region of a gene
How do steroid hormone-receptor complexes exert their effects?
I. They enter the nucleus to exert their effect
II. They bind to hormone-responsive elements on the promoters or
enhancers of the genes they up-regulate
III. They activate G protein-coupled receptors
IV. They activate transmembrane receptors
A. I and IV
B. II, III, and IV
C. II and III
D. I and II
E. I, II, and III
-Answer-D. I and II
The function of enhancers is an example of:
A. post-transcriptional mechanism for editing RNA
B. the stimulation of translation by initiation factors
C. an eukaryotic equivalent of prokaryotic promoter functioning
D. transcriptional control of gene expression
E. post-translational control that activates certain proteins
-Answer-D. transcriptional control of gene expression
Which of the following statements if TRUE regarding the regulation of
ferritin protein synthesis?
, A. when iron is abundant, the IRE-binding protein binds to iron-
responsive elements and stabilizes the mRNA that encodes ferritin
protein
B. the iron-responsive element serves as an enhancer to facilitate the
transcription of transferrin-receptor
C. the iron-responsive element is in the 3' untranslated region of the
mRNA that encodes ferritin protein
D. when iron is abundant, the IRE-binding protein binds to iron-
responsive element and allows the translation of ferritin protein
E. when iron is scarce, the IRE-binding protein binds to iron-responsive
element and stabilizes the mRNA that encodes ferritin protein
-Answer-D. when iron is abundant, the IRE-binding protein binds to
iron-responsive element and allows the translation of ferritin protein
In terms of epigenetic regulation of gene expression, acetylated histones
usually result in which of the following?
A. increase in transcription/gene expression
B. production and assembly of ribosomes
C. increase in DNA-histone association
D. decrease in transcription/gene expression
E. increase in DNA methylation
-Answer-A. increase in transcription/gene expression
Fragile X syndrome is due to the insertion of trinucleotide repeats
(CGG) into the 5' untranslated region of FMR1 gene. This insertion
results in:
A. aggregation of the unstable FMR1 proteins
B. prevention of initiation of protein translation
C. prevention of DNA unwinding for the transcription initiation
D. a nonsense mutation which causes the termination of translation
E. a decrease in mRNA synthesis due to DNA methylation
-Answer-E. a decrease in mRNA synthesis due to DNA methylation
DNA ligase functions by creating ____________ bonds between DNA
fragments or nucleotides.
EXAM QUESTIONS AND ACCURATE VERIFIED
ANSWERS/100%PASS/GRADED A+
The major interaction stabilizing the double helical structure of DNA is:
A. hydrogen bonds between bases on the two strands
B. covalent bonds that crosslink the two strands
C. van der Waals interactions between the stacked bases of the double
helix
D. the favorable charge-charge interactions between the two strands
E. hydrogen bonding between the backbone components of the two
strands
-Answer-A. hydrogen bonds between bases on the two strands
In regards to the lac operon in the presence of lactose, will the genes be
transcribed in large amounts?
A. yes; the lactose sugars remove the repressor and the genes will be
transcribed rigorously
B. yes; the lactose sugars bind transcription factors that turn on
transcription
C. no; the lactose sugars do not remove the repressor and the genes will
not be transcribed
D. no; the lac operon does not utilize lactose sugars in its regulatory
mechanism
E. maybe; it depends on the concentration of glucose
-Answer-E. maybe; it depends on the concentration of glucose
In eukaryotes, DNA is present in a chromatin structure. Chromatin is
made up of:
A. DNA that is highly compacted by compartmentalization in a series of
vesicles
B. DNA that is highly compacted by interaction with itself
C. DNA that is tightly associated with the inner face of the nuclear
membrane
,D. DNA that is highly compacted by supercoiling
E. DNA that is highly ordered by wrapping around histones
-Answer-E. DNA that is highly ordered by wrapping around histones
What is the typical location of a promoter in a gene?
A. upstream of the coding region of a gene
B. in the 3' UTR (untranslated region)
C. in the middle of the coding region of a gene
D. downstream of the coding region of a gene
-Answer-A. upstream of the coding region of a gene
How do steroid hormone-receptor complexes exert their effects?
I. They enter the nucleus to exert their effect
II. They bind to hormone-responsive elements on the promoters or
enhancers of the genes they up-regulate
III. They activate G protein-coupled receptors
IV. They activate transmembrane receptors
A. I and IV
B. II, III, and IV
C. II and III
D. I and II
E. I, II, and III
-Answer-D. I and II
The function of enhancers is an example of:
A. post-transcriptional mechanism for editing RNA
B. the stimulation of translation by initiation factors
C. an eukaryotic equivalent of prokaryotic promoter functioning
D. transcriptional control of gene expression
E. post-translational control that activates certain proteins
-Answer-D. transcriptional control of gene expression
Which of the following statements if TRUE regarding the regulation of
ferritin protein synthesis?
, A. when iron is abundant, the IRE-binding protein binds to iron-
responsive elements and stabilizes the mRNA that encodes ferritin
protein
B. the iron-responsive element serves as an enhancer to facilitate the
transcription of transferrin-receptor
C. the iron-responsive element is in the 3' untranslated region of the
mRNA that encodes ferritin protein
D. when iron is abundant, the IRE-binding protein binds to iron-
responsive element and allows the translation of ferritin protein
E. when iron is scarce, the IRE-binding protein binds to iron-responsive
element and stabilizes the mRNA that encodes ferritin protein
-Answer-D. when iron is abundant, the IRE-binding protein binds to
iron-responsive element and allows the translation of ferritin protein
In terms of epigenetic regulation of gene expression, acetylated histones
usually result in which of the following?
A. increase in transcription/gene expression
B. production and assembly of ribosomes
C. increase in DNA-histone association
D. decrease in transcription/gene expression
E. increase in DNA methylation
-Answer-A. increase in transcription/gene expression
Fragile X syndrome is due to the insertion of trinucleotide repeats
(CGG) into the 5' untranslated region of FMR1 gene. This insertion
results in:
A. aggregation of the unstable FMR1 proteins
B. prevention of initiation of protein translation
C. prevention of DNA unwinding for the transcription initiation
D. a nonsense mutation which causes the termination of translation
E. a decrease in mRNA synthesis due to DNA methylation
-Answer-E. a decrease in mRNA synthesis due to DNA methylation
DNA ligase functions by creating ____________ bonds between DNA
fragments or nucleotides.
