Name
Chem 501 – Intro to Biochem
Exam IV – Ch. 9, 24-28
May 8, 2006
1.
The genetic code has all of the following characteristics except:
A)
B)
C)
D)
E)
2.
Histones are
A)
B)
C)
D)
E)
3.
.
coenzymes derived from histidine; enzymes.
topoisomerases; RNA.
acidic proteins; DNA.
basic proteins; DNA.
acidic proteins; RNA.
dispersive
conservative
semiconservative
liberal
none of the above
Small signal molecules that regulate transcription are not known to:
A)
B)
C)
D)
E)
5.
that are usually associated with
DNA is replicated by a ________________ mechanism.
A)
B)
C)
D)
E)
4.
It is degenerate.
It is read 3’ to 5’.
It is read from a fixed starting point without punctuation.
It is not overlapping.
A group of three bases codes for one amino acid.
cause activator proteins to bind to DNA sites.
cause repressor proteins to bind to DNA sites.
directly bind to DNA sites.
prevent activator proteins from binding to DNA sites.
release repressor proteins from DNA sites.
The sequences in eukaryotic DNA known as introns are:
A)
B)
C)
D)
E)
those included in the final sequence of messenger RNA.
the intervening sequences not expressed in the final sequence of messenger RNA.
the binding sites for DNA polymerase.
the binding sites for RNA polymerase to initiate transcription.
the binding sites for RNA polymerase to terminate transcription.
1
6.
Which of the following statements about the polymerase chain reaction (PCR) is false?
A) DNA is amplified at many points within a cellular genome.
B) The boundaries of the amplified DNA segment are determined by the synthetic
oligonucleotides used to prime DNA synthesis.
C) The technique is sufficiently sensitive that DNA sequences can be amplified from a
single animal or human hair.
D) Newly synthesized DNA must be denatured with heat before the next round of DNA
synthesis begins.
E) DNA amplified by PCR can be cloned.
7.
It is correct to say that DNA supercoiling can:
A)
B)
C)
D)
E)
8.
be induced by strand separation.
be induced by underwinding of the double helix.
occur if a closed circular double-stranded DNA molecule has a nick.
result in compaction of the DNA structure.
A), B) and D) are all true.
Which of the following statements about tRNA molecules is false?
A) A, C, G, and U are the only bases present in the molecule.
B) Although composed of a single strand of RNA, each molecule contains several short,
double-helical regions.
C) Any given tRNA will accept only one specific amino acid.
D) The amino acid attachment is always to an A nucleotide at the 3’ end of the molecule.
E) There is at least one tRNA for each of the 20 amino acids.
9.
All of the following are characteristics for in vitro DNA synthesis except:
A)
B)
C)
D)
E)
10.
DNA polymerase adds nucleotides in a 5’→3’ direction.
The primer strand of DNA determines the nucleotides added.
Correct hydrogen bonding is the primary check of the newly synthesized DNA.
A primer strand must contain a free 3’-OH.
DNA polymerase copies the complementary strand of DNA.
Termination of translation in prokaryotic cells requires:
A) binding of the terminator tRNA to the termination codon.
B) interaction of release factors with the termination codon.
C) ternary interaction of the release factor and the termination tRNA with the
termination codon.
D) release factor interaction with the Shine-Dalgarno sequence and subsequent
dissociation of the two ribosomal subunits.
E) none of the above.
2
11.
Attenuation in the trp operon of E. coli:
A) can adjust transcription of the structural genes upwards when tryptophan is present.
B) can fine-tune the transcription of the operon in response to small changes in
tryptophan availability.
C) is a mechanism for inhibiting translation of existing (complete) trp mRNAs.
D) results from the binding of the Trp repressor to the operator.
E) results from the presence of short leader peptides at the 5’ end of each structural gene.
12.
At the replication forks in E. coli:
A)
B)
C)
D)
E)
13.
DNA helicases unwind DNA to allow strand separation.
DNA binding proteins stabilize the single stranded DNA.
DNA gyrase relieves the stress in the DNA molecule caused by strand separation.
RNA primers on the lagging strand are synthesized by primase.
all of the above.
Which of the following is a feature of the wobble hypothesis?
A) A tRNA can read only one codon.
B) Some tRNAs can read codons that specify two different amino acids, although both
amino acids are always nonpolar.
C) The third base in a codon is always a normal Watson-Crick base pair.
D) The “wobble” occurs only in the first base of the anticodon.
E) A naturally occuring tRNA exists in yeast that can read both arginine and lysine
codons.
14.
When a region of DNA must be repaired by removing and replacing some of the
nucleotides, what ensures that the new nucleotides are in the correct sequence?
A) DNA cannot be repaired and this explains why mutations occur.
B) Specific enzymes bind the correct nucleotides.
C) The new nucleotides base pair accurately with those on the complementary strand.
D) The repair enzyme recognizes the removed nucleotide and brings in an identical one
to replace it.
E) The three-dimensional structure determines the order of nucleotides.
15.
Which of the following statements regarding plasmid cloning vectors is false?
A) They are small, circular DNAs (often a few thousand base pairs long).
B) Foreign DNA fragments up to 100,000 base pairs can be cloned in a typical plasmid.
C) Plasmids often contain genes that confer resistance to antibiotics.
D) An origin of replication must be included in a plasmid to allow it to be propagated in
E. coli.
E) There may be multiple copies of a plasmid in a single host cell.
3
16.
The tryptophan operon of E. coli is repressed by tryptophan added to the growth medium.
The tryptophan repressor probably:
A)
B)
C)
D)
E)
17.
Formation of the 70S ribosomal initiation complex for bacterial protein synthesis does
not require:
A)
B)
C)
D)
E)
18.
binds to RNA polymerase when tryptophan is present.
binds to the trp operator in the absence of tryptophan.
binds to the trp operator in the presence of tryptophan.
is a DNA sequence.
is an attenuator.
fMet-tRNAfMet.
IF-2.
GTP.
mRNA.
EF-Tu.
Which of the following statements about E. coli RNA polymerase (core enzyme) is false?
A) The RNA product is complementary to the DNA template.
B) The RNA chain grows in a 53 direction.
C) The core enzyme has no polymerizing activity until the  (sigma) subunit is bound.
D) In the absence of the  subunit, core polymerase has little or no specificity for where
initiation begins.
E) The core enzyme contains several different subunits.
19.
The 5’→3’ exonuclease activity of E. coli DNA polymerase I is involved in:
A)
B)
C)
D)
E)
20.
formation of a nick at the DNA replication origin.
formation of Okazaki fragments.
proofreading of the replication process.
removal of RNA primers by nick translation.
sealing of nicks by ligase action.
All are required to perform in vitro cloning to produce a cDNA library of an eukaryote
except:
A)
B)
C)
D)
E)
DNA ligase.
a vector such as a plasmid.
restriction endonuclease.
mRNA.
all of the above are required.
4
21.
Under what conditions is the E. coli lac operon expressed?
A)
B)
C)
D)
E)
22.
All are common forms of DNA damage except:
A)
B)
C)
D)
E)
23.
replication errors resulting in a missing or incorrect base.
bulges due to deletions or insertions.
UV-induced base alterations, such as pyrimidine dimers.
strand breaks at phosphodiester bonds or within deoxyribose rings.
all of the above.
An RNA-dependent DNA polymerase that carries the RNA template with it to synthesize
repeats at the 3’-ends of linear chromosomes is called:
A)
B)
C)
D)
E)
24.
When glucose and lactose concentrations are low.
When lactose concentrations are low and glucose concentrations are high.
When glucose concentrations are low and lactose concentrations are high.
When glucose concentrations are low and galactose concentrations are high.
When glucose and lactose concentrations are high.
DNA ligase.
telomerase.
DNA polymerase  (gamma).
topoisomerase.
DNA polymerase  (beta).
Restriction enzymes:
A) are very specific proteases that cleave peptides at only certain sequences.
B) are highly specialized ribonucleases that degrade mRNA soon after its synthesis.
C) are sequence-specific DNA endonucleases.
D) catalyze the addition of a certain amino acid to a specific tRNA.
E) act at the membrane to restrict the passage of certain molecules into the cell.
25.
Which of the following statements about ribosomes is true?
A)
B)
C)
D)
E)
There are two major subunits, each with multiple proteins.
They are relatively small, with molecular weights less than 10,000.
The large subunit contains rRNA molecules, the small subunit does not.
There are about 25 of them in an E. coli cell.
They have specific, different binding sites for each of the 20 tRNAs.
5
26.
The large structure consisting of a mRNA molecule being translated by multiple copies
of the macromolecular complexes that carry out protein synthesis is called a :
A)
B)
C)
D)
E)
27.
Compared with DNA polymerase, reverse transcriptase:
A)
B)
C)
D)
E)
28.
proteolytic processing.
formation of disulfide bonds.
attachment of carbohydrate residues.
covalent modification of internal amino acids.
all of the above.
How is the rate of ribosomal protein synthesis kept in balance with rRNA availability?
A)
B)
C)
D)
E)
30.
makes fewer errors in synthesizing a complementary polynucleotide.
makes more errors, because it lacks the 35 proofreading exonuclease activity.
introduces no errors into genetic material, because it synthesizes RNA, not DNA.
synthesizes complementary strands in the opposite direction - from 35.
does not require a primer to initiate synthesis.
Posttranslational processing may involve:
A)
B)
C)
D)
E)
29.
lysosome.
polysome.
proteosome.
ribosome.
synthosome.
rRNAs stimulate the transcription of ribosomal protein operons.
Ribosomal proteins inhibit the translation of the mRNAs that encode them.
Ribosomal proteins activate the repressor of ribosomal protein operons.
Ribosomal proteins act as transactivators of rRNA genes.
Ribosomal proteins activate the repressor of rRNA operons.
The binding of CRP (cAMP receptor protein of E. coli) to DNA in the lac operon:
A)
B)
C)
D)
E)
assists RNA polymerase binding to the lac promoter.
is inhibited by a high level of cAMP.
occurs in the lac repressor region.
occurs only when glucose is present in the growth medium.
prevents repressor from binding to the lac operator.
6
31.
A regulatory protein that inhibits transcription is called a(n) :
A regulatory protein that facilitates transcription is called a(n) :
The process whereby transcription is initiated normally but is abruptly halted before the
operon genes are transcribed is called :
32.
UUU
UUC
UUA
UUG
CUU
CUC
CUA
CUG
AUU
AUC
AUA
AUG
GUU
GUC
GUA
GUG
Write down all the possible mRNA sequences that code for the simple tripeptide segment
HisTrpLys.
Phe
Phe
Leu
Leu
Leu
Leu
Leu
Leu
Ile
Ile
Ile
Met
Val
Val
Val
Val
UCU
UCC
UCA
UCG
CCU
CCC
CCA
CCG
ACU
ACC
ACA
ACG
GCU
GCC
GCA
GCG
Standard Genetic Code
Ser
UAU
Ser
UAC
Ser
UAA
Ser
UAG
Pro
CAU
Pro
CAC
Pro
CAA
Pro
CAG
Thr
AAU
Thr
AAC
Thr
AAA
Thr
AAG
Ala
GAU
Ala
GAC
Ala
GAA
Ala
GAG
Tyr
Tyr
Stop
Stop
His
His
Gln
Gln
Asn
Asn
Lys
Lys
Asp
Asp
Glu
Glu
UGU
UGC
UGA
UGG
CGU
CGC
CGA
CGG
AGU
AGC
AGA
AGG
GGU
GGC
GGA
GGG
Cys
Cys
Stop
Trp
Arg
Arg
Arg
Arg
Ser
Ser
Arg
Arg
Gly
Gly
Gly
Gly
7
8