Metabolic Biochemistry BIOC 385 Exam 4 Review Test
Bank A- 250 Latest Real Exam Questions and Correct
Verified Answers/ BIOC 385 Exam 4 Latest 2026-2027
University of Arizona/ Biochem 385 Exam 4
When there are high levels of tryptophan in the bacterial cell, the effect it has on
the Trp repressor is _______________ and the effect on the structure of the Trp
operon mRNA is _____________.
A. To stimulate operon binding; to promote formation of the regions 2-3 stem loop
B. To inhibit operon binding; to promote formation of the regions 3-4 stem loop
C. To stimulate operon binding; to promote formation of the regions 3-4 stem loop
D. To inhibit operon binding; to promote formation of the regions 2-3 stem loop
-ANSWER- C
An Ames test of a compound suspected to be a mutagen was examined before and
after incubation with rat liver extract. Based on the results shown, what do you
conclude?
A. The Ames test does not work considering the liver is worse
B. The control plate shows low mutation rate, which is surprising
C. All three bacterial plates must contain a large amount of histidine to prevent
colonies from forming
D. Compound is not mutagenic at all because colonies grow meaning that their
DNA is undamaged
E. Compound is mutagenic without liver enzymes and this activity is further
1
,enhanced by liver enzymes
-ANSWER- E
Which chromatin modification in eukaryotes is associated with activation of gene
transcription?
A. Close packing of nucleosomes to form regions of chromatin condensation in the
enhancer region
B. Deacetylation of lysine residues on histone proteins by the enzyme histone
deacetylase
C. Binding of insulator proteins on the DNA between the gene promoter and the
enhancer region
D. Acetylation of lysine residues on histone proteins by the enzyme histone
acetyltransferase
E. Phosphorylation of the chromatin remodeling ISWI complex causing
nucleosome stacking on DNA
-ANSWER- D
Match the description of each mode of regulation with the illustration diagrammed
at the right and record your answer in the order 1. Ligand-regulated de-repression
2. Ligand-regulated repression 3. Ligand-regulated activation 4. Ligand-regulated
de-activation
A. BADC
B. ABCD
C. CDAB
D. DCBA
-ANSWER- A
2
,Lynch syndrome is a human genetic disease characterized by ~100-fold higher
incidence of colon cancer in men and women - and uterine cancer in women - by
the age 50, as compared to the general population. Which statement below best
describes the genetic cause of Lynch syndrome.
A. Lynch syndrome is caused by defects in the human nucleotide excision repair
genes hUvrA and hUvrC
B. Lynch syndrome is caused by defects in the human thymine dimer repair
enzyme photolyase
C. Lynch syndrome is caused by defects in the human mismatch repair enzymes
hMLH1 and hMSH2
D. Lynch syndrome is caused by defects in the human resolvase enzyme and
excess Holliday junctions
E. Lynch syndrome is caused by defects in the human base excision repair enzyme
uracil DNA glycosylase
-ANSWER- C
Based on the sequence of the double stranded DNA shown above, which sequence
below corresponds to the mRNA transcript?
A. 5'-GCGUAUAGCGAAA-3'
B. 3'-CGCUAUAGCGUUU-5'
C. 5'-CGCUAUAGCGUUU-3'
D. 5'-AAAGCGAUAUCGC-3'
E. 5'-UUUGCGAUAUCGC-3'
-ANSWER- C
Why does RNA contain uracil and DNA contain thymine?
A. RNA transcription base pairs U-T in the RNA with DNA, whereas this process
base pairs A-T in the RNA with DNA. Therefore, if uracil were present in DNA,
then U-A and A-U could not be distinguished
B. Loss of NH3 from cytosine generates uracil, which base pairs with thymine and
cause damage in DNA. If deamination of thymine generated guanine, then this
would not be a problem
C. DNA damage can alter the nucleotide bases and cause mutations that cannot be
repaired if the base is uracil since repair enzymes recognize thymine in DNA, not
3
, uracil
D. Uracil specifies RNA polymerization, and therefore, if uracil is inserted into
DNA, then RNA polymerization will occur on DNA strands
E. Spontaneous cytosine deamination generates uracil, which base pairs with
adenine during replication, and thereby converts a C-G base pair to a T-A base pair
-ANSWER- E
T/F Prokaryotic and eukaryotic ribosomes both contain RNA that functions as a
catalytic enzyme.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F The wobble position in tRNA is 5' nucleotide in the anti-codon and 3'
nucleotide in mRNA codon.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F Ribosomal E, P, and A sites align tRNA anti-codons with the corresponding
mRNA codons.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F Accurate protein synthesis requires tRNA synthetases to link GTP to 3' end of
tRNA molecules.
A. True
B. False
C. Only prokaryotic
4
Bank A- 250 Latest Real Exam Questions and Correct
Verified Answers/ BIOC 385 Exam 4 Latest 2026-2027
University of Arizona/ Biochem 385 Exam 4
When there are high levels of tryptophan in the bacterial cell, the effect it has on
the Trp repressor is _______________ and the effect on the structure of the Trp
operon mRNA is _____________.
A. To stimulate operon binding; to promote formation of the regions 2-3 stem loop
B. To inhibit operon binding; to promote formation of the regions 3-4 stem loop
C. To stimulate operon binding; to promote formation of the regions 3-4 stem loop
D. To inhibit operon binding; to promote formation of the regions 2-3 stem loop
-ANSWER- C
An Ames test of a compound suspected to be a mutagen was examined before and
after incubation with rat liver extract. Based on the results shown, what do you
conclude?
A. The Ames test does not work considering the liver is worse
B. The control plate shows low mutation rate, which is surprising
C. All three bacterial plates must contain a large amount of histidine to prevent
colonies from forming
D. Compound is not mutagenic at all because colonies grow meaning that their
DNA is undamaged
E. Compound is mutagenic without liver enzymes and this activity is further
1
,enhanced by liver enzymes
-ANSWER- E
Which chromatin modification in eukaryotes is associated with activation of gene
transcription?
A. Close packing of nucleosomes to form regions of chromatin condensation in the
enhancer region
B. Deacetylation of lysine residues on histone proteins by the enzyme histone
deacetylase
C. Binding of insulator proteins on the DNA between the gene promoter and the
enhancer region
D. Acetylation of lysine residues on histone proteins by the enzyme histone
acetyltransferase
E. Phosphorylation of the chromatin remodeling ISWI complex causing
nucleosome stacking on DNA
-ANSWER- D
Match the description of each mode of regulation with the illustration diagrammed
at the right and record your answer in the order 1. Ligand-regulated de-repression
2. Ligand-regulated repression 3. Ligand-regulated activation 4. Ligand-regulated
de-activation
A. BADC
B. ABCD
C. CDAB
D. DCBA
-ANSWER- A
2
,Lynch syndrome is a human genetic disease characterized by ~100-fold higher
incidence of colon cancer in men and women - and uterine cancer in women - by
the age 50, as compared to the general population. Which statement below best
describes the genetic cause of Lynch syndrome.
A. Lynch syndrome is caused by defects in the human nucleotide excision repair
genes hUvrA and hUvrC
B. Lynch syndrome is caused by defects in the human thymine dimer repair
enzyme photolyase
C. Lynch syndrome is caused by defects in the human mismatch repair enzymes
hMLH1 and hMSH2
D. Lynch syndrome is caused by defects in the human resolvase enzyme and
excess Holliday junctions
E. Lynch syndrome is caused by defects in the human base excision repair enzyme
uracil DNA glycosylase
-ANSWER- C
Based on the sequence of the double stranded DNA shown above, which sequence
below corresponds to the mRNA transcript?
A. 5'-GCGUAUAGCGAAA-3'
B. 3'-CGCUAUAGCGUUU-5'
C. 5'-CGCUAUAGCGUUU-3'
D. 5'-AAAGCGAUAUCGC-3'
E. 5'-UUUGCGAUAUCGC-3'
-ANSWER- C
Why does RNA contain uracil and DNA contain thymine?
A. RNA transcription base pairs U-T in the RNA with DNA, whereas this process
base pairs A-T in the RNA with DNA. Therefore, if uracil were present in DNA,
then U-A and A-U could not be distinguished
B. Loss of NH3 from cytosine generates uracil, which base pairs with thymine and
cause damage in DNA. If deamination of thymine generated guanine, then this
would not be a problem
C. DNA damage can alter the nucleotide bases and cause mutations that cannot be
repaired if the base is uracil since repair enzymes recognize thymine in DNA, not
3
, uracil
D. Uracil specifies RNA polymerization, and therefore, if uracil is inserted into
DNA, then RNA polymerization will occur on DNA strands
E. Spontaneous cytosine deamination generates uracil, which base pairs with
adenine during replication, and thereby converts a C-G base pair to a T-A base pair
-ANSWER- E
T/F Prokaryotic and eukaryotic ribosomes both contain RNA that functions as a
catalytic enzyme.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F The wobble position in tRNA is 5' nucleotide in the anti-codon and 3'
nucleotide in mRNA codon.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F Ribosomal E, P, and A sites align tRNA anti-codons with the corresponding
mRNA codons.
A. True
B. False
C. Only prokaryotic
D. Only eukaryotic
-ANSWER- A
T/F Accurate protein synthesis requires tRNA synthetases to link GTP to 3' end of
tRNA molecules.
A. True
B. False
C. Only prokaryotic
4
