1) Which of the following variations on translation would
be most disadvantageous for a cell?
A) translating polypeptides directly from DNA
B) using fewer kinds of tRNA
C) having only one stop codon
D) lengthening the half-life of mRNA
E) having a second codon (besides AUG) as a start codon
Answer: A
2) Garrod hypothesized that "inborn errors of
metabolism" such as alkaptonuria occur because
A) metabolic enzymes require vitamin cofactors, and
affected individuals have significant nutritional deficiencies.
B) enzymes are made of DNA, and affected individuals lack
DNA polymerase.
C) many metabolic enzymes use DNA as a cofactor, and
affected individuals have mutations that prevent their enzymes from interacting
efficiently with DNA.
D) certain metabolic reactions are carried out by
ribozymes, and affected individuals lack key splicing factors.
E) genes dictate the production of specific enzymes, and
affected individuals have genetic defects that cause them to lack certain
enzymes.
Answer: A
3) Garrod's information about the enzyme alteration
resulting in alkaptonuria led to further elucidation of the same pathway in
humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is
altered or missing, resulting in a failure of phenylalanine (phe) to be
metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate
in the pathway altered in alkaptonuria. How might PKU affect the presence or
absence of alkaptonuria?
A) It would have no effect, because PKU occurs several steps
away in the pathway.
B) It would have no effect, because tyrosine is also
available from the diet.
C) Anyone with PKU must also have alkaptonuria.
D) Anyone with PKU is born with a predisposition to later
alkaptonuria.
E) Anyone with PKU has mild symptoms of alkaptonuria.
Answer: B
4) The nitrogenous base adenine is found in all members
of which group?
A) proteins, triglycerides, and testosterone
B) proteins, ATP, and DNA
C) ATP, RNA, and DNA
D) α glucose, ATP, and DNA
E) proteins, carbohydrates, and ATP
Answer: C
5) A particular triplet of bases in the template strand
of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is
A) 3' UCA 5'.
B) 3' UGA 5'.
C) 5' TCA 3'.
D) 3' ACU 5'.
E) either UCA or TCA, depending on wobble in the first
base.
Answer: A
6) The genetic code is essentially the same for all
organisms. From this, one can logically assume which of the following?
A) A gene from an organism can theoretically be expressed
by any other organism.
B) All organisms have experienced convergent evolution.
C) DNA was the first genetic material.
D) The same codons in different organisms translate into
the different amino acids.
E) Different organisms have different numbers of
different types of amino acids.
Answer: A
7) The "universal" genetic code is now known to
have exceptions. Evidence for this can be found if which of the following is
true?
A) If UGA, usually a stop codon, is found to code for an
amino acid such as tryptophan (usually coded for by UGG only).
B) If one stop codon, such as UGA, is found to have a
different effect on translation than another stop codon, such as UAA.
C) If prokaryotic organisms are able to translate a
eukaryotic mRNA and produce the same polypeptide.
D) If several codons are found to translate to the same
amino acid, such as serine.
E) If a single mRNA molecule is found to translate to
more than one polypeptide when there are two or more AUG sites.
Answer: A
8) Which of the following nucleotide triplets best represents
a codon?
A) a triplet separated spatially from other triplets
B) a triplet that has no corresponding amino acid
C) a triplet at the opposite end of tRNA from the
attachment site of the amino acid
D) a triplet in the same reading frame as an upstream AUG
E) a sequence in tRNA at the 3' end
Answer: D
9) Which of the following provides some evidence that RNA
probably evolved before DNA?
A) RNA polymerase uses DNA as a template.
B) RNA polymerase makes a single-stranded molecule.
C) RNA polymerase does not require localized unwinding of
the DNA.
D) DNA polymerase uses primer, usually made of RNA.
E) DNA polymerase has proofreading function.
Answer: D
10) Which of the following statements best describes the
termination of transcription in prokaryotes?
A) RNA polymerase transcribes through the polyadenylation
signal, causing proteins to associate with the transcript and cut it free from
the polymerase.
B) RNA polymerase transcribes through the terminator
sequence, causing the polymerase to separate from the DNA and release the
transcript.
C) RNA polymerase transcribes through an intron, and the
snRNPs cause the polymerase to let go of the transcript.
D) Once transcription has initiated, RNA polymerase
transcribes until it reaches the end of the chromosome.
E) RNA polymerase transcribes through a stop codon,
causing the polymerase to stop advancing through the gene and release the mRNA.
Answer: B
11) Which of the following does not occur in prokaryotic
eukaryotic gene expression, but does in eukaryotic gene expression?
A) mRNA, tRNA, and rRNA are transcribed.
B) RNA polymerase binds to the promoter.
C) A poly-A tail is added to the 3' end of an mRNA and a
cap is added to the 5' end.
D) Transcription can begin as soon as translation has
begun even a little.
E) RNA polymerase requires a primer to elongate the
molecule.
Answer: C
12) RNA polymerase in a prokaryote is composed of several
subunits. Most of these subunits are the same for the transcription of any
gene, but one, known as sigma, varies considerably. Which of the following is
the most probable advantage for the organism of such sigma switching?
A) It might allow the transcription process to vary from
one cell to another.
B) It might allow the polymerase to recognize different
promoters under certain environmental conditions.
C) It could allow the polymerase to react differently to
each stop codon.
D) It could allow ribosomal subunits to assemble at
faster rates.
E) It could alter the rate of translation and of exon
splicing.
Answer: B
13) Which of the following is a function of a poly-A
signal sequence?
A) It adds the poly-A tail to the 3' end of the mRNA.
B) It codes for a sequence in eukaryotic transcripts that
signals enzymatic cleavage ~1035 nucleotides away.
C) It allows the 3' end of the mRNA to attach to the
ribosome.
D) It is a sequence that codes for the hydrolysis of the
RNA polymerase.
E) It adds a 7-methylguanosine cap to the 3' end of the
mRNA.
Answer: B
14) In eukaryotes there are several different types of
RNA polymerase. Which type is involved in transcription of mRNA for a globin
protein?
A) ligase
B) RNA polymerase I
C) RNA polymerase II
D) RNA polymerase III
E) primase
Answer: C
15) Transcription in eukaryotes requires which of the
following in addition to RNA polymerase?
A) the protein product of the promoter
B) start and stop codons
C) ribosomes and tRNA
D) several transcription factors (TFs)
E) aminoacyl synthetase
Answer: D
16) A part of the promoter, called the TATA box, is said
to be highly conserved in evolution. Which of the following might this
illustrate?
A) The sequence evolves very rapidly.
B) The sequence does not mutate.
C) Any mutation in the sequence is selected against.
D) The sequence is found in many but not all promoters.
E) The sequence is transcribed at the start of every
gene.
Answer: C
17) The TATA sequence is found only several nucleotides
away from the start site of transcription. This most probably relates to which
of the following?
A) the number of hydrogen bonds between A and T in DNA
B) the triplet nature of the codon
C) the ability of this sequence to bind to the start site
D) the supercoiling of the DNA near the start site
E) the 3-D shape of a DNA molecule
Answer: A
18) What is a ribozyme?
A) an enzyme that uses RNA as a substrate
B) an RNA with enzymatic activity
C) an enzyme that catalyzes the association between the
large and small ribosomal subunits
D) an enzyme that synthesizes RNA as part of the
transcription process
E) an enzyme that synthesizes RNA primers during DNA
replication
Answer: B
19) A transcription unit that is 8,000 nucleotides long
may use 1,200 nucleotides to make a protein consisting of approximately 400
amino acids. This is best explained by the fact that
A) many noncoding stretches of nucleotides are present in
mRNA.
B) there is redundancy and ambiguity in the genetic code.
C) many nucleotides are needed to code for each amino
acid.
D) nucleotides break off and are lost during the
transcription process.
E) there are termination exons near the beginning of
mRNA.
Answer: A
20) During splicing, which molecular component of the
spliceosome catalyzes the excision reaction?
A) protein
B) DNA
C) RNA
D) lipid
E) sugar
Answer: C
21) Alternative RNA splicing
A) is a mechanism for increasing the rate of
transcription.
B) can allow the production of proteins of different
sizes from a single mRNA.
C) can allow the production of similar proteins from
different RNAs.
D) increases the rate of transcription.
E) is due to the presence or absence of particular
snRNPs.
Answer: B
22) In the structural organization of many eukaryotic
genes, individual exons may be related to which of the following?
A) the sequence of the intron that immediately precedes
each exon
B) the number of polypeptides making up the functional
protein
C) the various domains of the polypeptide product
D) the number of restriction enzyme cutting sites
E) the number of start sites for transcription
Answer: C
23) In an experimental situation, a student researcher
inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap
and poly-A tail. Which of the following would you expect him to find?
A) The mRNA could not exit the nucleus to be translated.
B) The cell recognizes the absence of the tail and
polyadenylates the mRNA.
C) The molecule is digested by restriction enzymes in the
nucleus.
D) The molecule is digested by exonucleases since it is
no longer protected at the 5' end.
E) The molecule attaches to a ribosome and is translated,
but more slowly.
Answer: D
24. Use the following model of a eukaryotic transcript to
answer the next few questions.
5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3'
Which components of the previous molecule will also be
found in mRNA in the cytosol?
A) 5' UTR I₁ I₂ I₃ UTR 3'
B) 5' E₁ E₂ E₃ E₄ 3'
C) 5' UTR E₁ E₂ E₃ E₄ UTR 3'
D) 5' I₁ I₂ I₃ 3'
E) 5' E₁ I₁ E₂ I₂ E₃ I₃ E₄ 3'
Answer: C
25. Use the following model of a eukaryotic transcript to
answer the next few questions.
5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3'
When the spliceosome binds to elements of this structure,
where can it attach?
A) to the exons
B) to the 5' UTR
C) to the 3' UTR
D) to an adjacent intron and exon
E) to the end of an intron
Answer: E
26. Use the following model of a eukaryotic transcript to
answer the next few questions.
5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3'
Which of the following is a useful feature of introns for
this model?
A) They are translated into small polypeptides.
B) They become parts of snRNPs.
C) Each intron has enzymatic properties.
D) Introns allow exon shuffling.
E) Introns protect exon structure.
Answer: D
27. Use the following model of a eukaryotic transcript to
answer the next few questions.
5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3'
Suppose that exposure to a chemical mutagen results in a
change in the sequence that alters the 5' end of intron 1 (I₁). What might
occur?
A) loss of the gene product
B) loss of E₁
C) premature stop to the mRNA
D) inclusion of I₁ in the mRNA
E) exclusion of E₂
Answer: D
28. Use the following model of a eukaryotic transcript to
answer the next few questions.
5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3'
Suppose that an induced mutation removes most of the 5'
end of the 5' UTR. What might result?
A) Removal of the 5' UTR has no effect because the exons
are still maintained.
B) Removal of the 5' UTR also removes the 5' cap and the
mRNA will quickly degrade.
C) The 3' UTR will duplicate and one copy will replace
the 5' end.
D) The first exon will not be read because I₁ will now
serve as the UTR.
E) Removal of the 5' UTR will result in the strand not
binding to tRNAs.
Answer: B
29) A particular triplet of bases in the coding sequence
of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
A) TTT.
B) UUA.
C) UUU.
D) AAA.
E) either UAA or TAA, depending on first base wobble.
Answer: C
30) Accuracy in the translation of mRNA into the primary
structure of a polypeptide depends on specificity in the
A) binding of ribosomes to mRNA.
B) shape of the A and P sites of ribosomes.
C) bonding of the anticodon to the codon.
D) attachment of amino acids to tRNAs.
E) bonding of the anticodon to the codon and the
attachment of amino acids to tRNAs.
Answer: E
31) What is the function of GTP in translation?
A) GTP energizes the formation of the initiation complex,
using initiation factors.
B) GTP hydrolyzes to provide phosphate groups for tRNA
binding.
C) GTP hydrolyzes to provide energy for making peptide
bonds.
D) GTP supplies phosphates and energy to make ATP from
ADP.
E) GTP separates the small and large subunits of the
ribosome at the stop codon.
Answer: A
32) A mutant bacterial cell has a defective aminoacyl
synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of
the normal phenylalanine. The consequence of this for the cell will be that
A) none of the proteins in the cell will contain
phenylalanine.
B) proteins in the cell will include lysine instead of
phenylalanine at amino acid positions specified by the codon UUU.
C) the cell will compensate for the defect by attaching
phenylalanine to tRNAs with lysine-specifying anticodons.
D) the ribosome will skip a codon every time a UUU is
encountered.
E) none of the options will occur; the cell will
recognize the error and destroy the tRNA.
Answer: B
33) There are 61 mRNA codons that specify an amino acid,
but only 45 tRNAs. This is best explained by the fact that
A) some tRNAs have anticodons that recognize four or more
different codons.
B) the rules for base pairing between the third base of a
codon and tRNA are flexible.
C) many codons are never used, so the tRNAs that
recognize them are dispensable.
D) the DNA codes for all 61 tRNAs but some are then
destroyed.
E) competitive exclusion forces some tRNAs to be
destroyed by nucleases.
Answer: B
34) Which of the following is the first event to take
place in translation in eukaryotes?
A) elongation of the polypeptide
B) base pairing of activated methionine-tRNA to AUG of
the messenger RNA
C) binding of the larger ribosomal subunit to smaller
ribosomal subunits
D) covalent bonding between the first two amino acids
E) the small subunit of the ribosome recognizes and
attaches to the 5' cap of mRNA
Answer: E
35) Which of the following is a function of a signal
peptide?
A) to direct an mRNA molecule into the cisternal space of
the ER
B) to bind RNA polymerase to DNA and initiate
transcription
C) to terminate translation of the messenger RNA
D) to translocate polypeptides across the ER membrane
E) to signal the initiation of transcription
Answer: D
36) When translating secretory or membrane proteins,
ribosomes are directed to the ER membrane by
A) a specific characteristic of the ribosome itself,
which distinguishes free ribosomes from bound ribosomes.
B) a signal-recognition particle that brings ribosomes to
a receptor protein in the ER membrane.
C) moving through a specialized channel of the nucleus.
D) a chemical signal given off by the ER.
E) a signal sequence of RNA that precedes the start codon
of the message.
Answer: B
37) An experimenter has altered the 3' end of the tRNA
corresponding to the amino acid methionine in such a way as to remove the 3'
AC. Which of the following hypotheses describes the most likely result?
A) tRNA will not form a cloverleaf.
B) The nearby stem end will pair improperly.
C) The amino acid methionine will not bind.
D) The anticodon will not bind with the mRNA codon.
E) The aminoacylsynthetase will not be formed.
Answer: C
38) The process of translation, whether in prokaryotes or
eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the
following?
A) polypeptide factors plus ATP
B) polypeptide factors plus GTP
C) polymerases plus GTP
D) SRP plus chaperones
E) signal peptides plus release factor
Answer: B
39) When the ribosome reaches a stop codon on the mRNA,
no corresponding tRNA enters the A site. If the translation reaction were to be
experimentally stopped at this point, which of the following would you be able
to isolate?
A) an assembled ribosome with a polypeptide attached to
the tRNA in the P site
B) separated ribosomal subunits, a polypeptide, and free
tRNA
C) an assembled ribosome with a separated polypeptide
D) separated ribosomal subunits with a polypeptide
attached to the tRNA
E) a cell with fewer ribosomes
Answer: A
40) What is the function of the release factor (RF)?
A) It separates tRNA in the A site from the growing
polypeptide.
B) It binds to the stop codon in the A site in place of a
tRNA.
C) It releases the amino acid from its tRNA to allow the
amino acid to form a peptide bond.
D) It supplies a source of energy for termination of
translation.
E) It releases the ribosome from the ER to allow
polypeptides into the cytosol.
Answer: B
41) When the function of the newly made polypeptide is to
be secreted from the cell where it has been made, what must occur?
A) It must be translated by a ribosome that remains free
of attachment to the ER.
B) Its signal sequence must target it to the ER, from
which it goes to the Golgi.
C) It has a signal sequence that must be cleaved off
before it can enter the ER.
D) It has a signal sequence that targets it to the cell's
plasma membrane where it causes exocytosis.
E) Its signal sequence causes it to be encased in a
vesicle as soon as it is translated.
Answer: B
42) Suppose that a mutation alters the formation of a
tRNA such that it still attaches to the same amino acid (phe) but its anticodon
loop has the sequence AAU that binds to the mRNA codon UUA (that usually
specifies leucine leu).
A) The modified tRNA will cause this mRNA to make only
nonfunctioning product.
B) The tRNA-leu will not be able to enter the site of the
ribosome to bind to the UUA.
C) One mutated tRNA molecule will be relatively
inconsequential because it will compete with many "normal" ones.
D) The tRNA will be so unstable that it will not
participate in translation.
E) The mutated tRNA will result in an amino acid variant
in all copies of the protein.
Answer: C
43) Why might a point mutation in DNA make a difference
in the level of protein's activity?
A) It might result in a chromosomal translocation.
B) It might exchange one stop codon for another stop
codon.
C) It might exchange one serine codon for a different serine
codon.
D) It might substitute an amino acid in the active site.
E) It might substitute the N-terminus of the polypeptide
for the C-terminus.
Answer: D
44) In the 1920s Muller discovered that X-rays caused
mutation in Drosophila. In a related series of experiments in the 1940s,
Charlotte Auerbach discovered that chemicals–she used nitrogen mustards–have a
similar effect. A new chemical food additive is developed by a cereal
manufacturer. Why do we test for its ability to induce mutation?
A) We worry that it might cause mutation in cereal grain
plants.
B) We want to make sure that it does not emit radiation.
C) We want to be sure that it increases the rate of
mutation sufficiently.
D) We want to prevent any increase in mutation frequency.
E) We worry about its ability to cause infection.
Answer: D
45) Which of the following types of mutation, resulting
in an error in the mRNA just after the AUG start of translation, is likely to
have the most serious effect on the polypeptide product?
A) a deletion of a codon
B) a deletion of two nucleotides
C) a substitution of the third nucleotide in an ACC codon
D) a substitution of the first nucleotide of a GGG codon
E) an insertion of a codon
Answer: B
46) What is the effect of a nonsense mutation in a gene?
A) It changes an amino acid in the encoded protein.
B) It has no effect on the amino acid sequence of the
encoded protein.
C) It introduces a premature stop codon into the mRNA.
D) It alters the reading frame of the mRNA.
E) It prevents introns from being excised.
Answer: C
47) A frameshift mutation could result from
A) a base insertion only.
B) a base deletion only.
C) a base substitution only.
D) deletion of three consecutive bases.
E) either an insertion or a deletion of a base.
Answer: E
48) Which of the following DNA mutations is the most
likely to be damaging to the protein it specifies?
A) a base-pair deletion
B) a codon substitution
C) a substitution in the last base of a codon
D) a codon deletion
E) a point mutation
Answer: A
49) Which small-scale mutation would be most likely to
have a catastrophic effect on the functioning of a protein?
A) a base substitution
B) a base deletion near the start of a gene
C) a base deletion near the end of the coding sequence,
but not in the terminator codon
D) deletion of three bases near the start of the coding
sequence, but not in the initiator codon
E) a base insertion near the end of the coding sequence,
but not in the terminator codon
Answer: B
50) The most commonly occurring mutation in people with
cystic fibrosis is a deletion of a single codon. This results in
A) a base-pair substitution.
B) a nucleotide mismatch.
C) a frameshift mutation.
D) a polypeptide missing an amino acid.
E) a nonsense mutation.
Answer: D
51) Which of the following mutations is most likely to
cause a phenotypic change?
A) a duplication of all or most introns
B) a large inversion whose ends are each in intergenic
regions
C) a nucleotide substitution in an exon coding for a
transmembrane domain
D) a single nucleotide deletion in an exon coding for an
active site
E) a frameshift mutation one codon away from the 3' end
of the nontemplate strand
Answer: D
52) If a protein is coded for by a single gene and this
protein has six clearly defined domains, which number of exons below is the
gene likely to have?
A) 1
B) 5
C) 8
D) 12
E) 14
Answer: C
53) Which of the following statements is true about
protein synthesis in prokaryotes?
A) Extensive RNA processing is required before
prokaryotic transcripts can be translated.
B) Translation can begin while transcription is still in
progress.
C) Prokaryotic cells have complicated mechanisms for
targeting proteins to the appropriate cellular organelles.
D) Translation requires antibiotic activity.
E) Unlike eukaryotes, prokaryotes require no initiation
or elongation factors.
Answer: B
54) Of the following, which is the most current
description of a gene?
A) a unit of heredity that causes formation of a
phenotypic characteristic
B) a DNA subunit that codes for a single complete protein
C) a DNA sequence that is expressed to form a functional
product: either RNA or polypeptide
D) a DNA—RNA sequence combination that results in an
enzymatic product
E) a discrete unit of hereditary information that
consists of a sequence of amino acids
Answer: C
55) Gene expression in the domain Archaea in part
resembles that of bacteria and in part that of the domain Eukarya. In which way
is it most like the domain Eukarya?
A) Domain Archaea have numerous transcription factors.
B) Initiation of translation is like that of domain
Eukarya.
C) There is only one RNA polymerase.
D) Transcription termination often involves attenuation.
E) Post-transcriptional splicing is like that of Eukarya.
Answer: A
56) Which of the following is true of transcription in
domain Archaea?
A) It is regulated in the same way as in domain Bacteria.
B) There is only one kind of RNA polymerase.
C) It is roughly simultaneous with translation.
D) Promoters are identical to those in domain Eukarya.
E) It terminates in a manner similar to bacteria.
Answer: C
57) In comparing DNA replication with RNA transcription
in the same cell, which of the following is true only of replication?
A) It uses RNA polymerase.
B) It makes a new molecule from its 5' end to its 3' end.
C) The process is extremely fast once it is initiated.
D) The process occurs in the nucleus of a eukaryotic
cell.
E) The entire template molecule is represented in the
product.
Answer: E
58) In order for a eukaryotic gene to be engineered into
a bacterial colony to be expressed, what must be included in addition to the
coding exons of the gene?
A) the introns
B) eukaryotic polymerases
C) a bacterial promoter sequence
D) eukaryotic ribosomal subunits
E) eukaryotic tRNAs
Answer: C
59) When the genome of a particular species is said to
include 20,000 protein-coding regions, what does this imply?
A) There are 20,000 genes.
B) Each gene codes for one protein.
C) Any other regions are "junk" DNA.
D) There are also genes for RNAs other than mRNA.
E) The species is highly evolved.
Answer: D
60) According to Beadle and Tatum's hypothesis, how many
genes are necessary for this pathway?
A) 0
B) 1
C) 2
D) 3
E) It cannot be determined from the pathway.
Answer: C
61) A mutation results in a defective enzyme A. Which of
the following would be a consequence of that mutation?
A) an accumulation of A and no production of B and C
B) an accumulation of A and B and no production of C
C) an accumulation of B and no production of A and C
D) an accumulation of B and C and no production of A
E) an accumulation of C and no production of A and B
Answer: A
62) If A, B, and C are all required for growth, a strain
that is mutant for the gene-encoding enzyme A would be able to grow on which of
the following media?
A) minimal medium
B) minimal medium supplemented with nutrient A only
C) minimal medium supplemented with nutrient B only
D) minimal medium supplemented with nutrient C only
E) minimal medium supplemented with nutrients A and C
Answer: C
63) If A, B, and C are all required for growth, a strain
mutant for the gene-encoding enzyme B would be capable of growing on which of
the following media?
A) minimal medium
B) minimal medium supplemented with A only
C) minimal medium supplemented with B only
D) minimal medium supplemented with C only
E) minimal medium supplemented with nutrients A and B
Answer: D
64) A possible sequence of nucleotides in the template
strand of DNA that would code for the polypeptide sequence phe-leu-ile-val
would be
A) 5' TTG-CTA-CAG-TAG 3'.
B) 3' AAC-GAC-GUC-AUA 5'.
C) 5' AUG-CTG-CAG-TAT 3'.
D) 3' AAA-AAT-ATA-ACA 5'.
E) 3' AAA-GAA-TAA-CAA 5'.
Answer: E
65) What amino acid sequence will be generated, based on
the following mRNA codon sequence?
5' AUG-UCU-UCG-UUA-UCC-UUG 3'
A) met-arg-glu-arg-glu-arg
B) met-glu-arg-arg-glu-leu
C) met-ser-leu-ser-leu-ser
D) met-ser-ser-leu-ser-leu
E) met-leu-phe-arg-glu-glu
Answer: D
66) A peptide has the sequence
NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the
coding strand of the DNA could code for this peptide?
A) 3' UUU-CCC-AAA-GGG-UUU-CCC
B) 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG
C) 5' TTT-CCC-AAA-GGG-TTT-CCC
D) 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG
E) 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA
Answer: C
DNA template strand
5' ____________________________ 3'
DNA complementary strand
3' ____________________________ 5'
67) Given the locally unwound double strand above, in
which direction does the RNA polymerase move?
A) 3' → 5' along the template strand
B) 5' → 3' along the template strand
C) 3' → 5' along the complementary strand
D) 5' → 3' along the complementary strand
E) 5' → 3' along the double-stranded DNA
Answer: A
• 68
DNA template strand
5' ____________________________ 3'
DNA complementary strand
3' ____________________________ 5'
68) In the transcription event of the previous DNA, where
would the promoter be located?
A) at the 3' end of the newly made RNA
B) to the right of the template strand
C) to the left of the template strand
D) to the right of the sense strand
E) to the left of the sense strand
Answer: B
69. A part of an mRNA molecule with the following sequence is
being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer
RNA molecules (with their anticodons shown in the 3' to 5' direction) are available.
Two of them can correctly match the mRNA so that a dipeptide can form.
The dipeptide that will form will be
A) cysteine-alanine.
B) proline-threonine.
C) glycine-cysteine.
D) alanine-alanine.
E) threonine-glycine.
Answer: B
70. A part of an mRNA molecule with the following
sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following
charged transfer RNA molecules (with their anticodons shown in the 3' to 5'
direction) are available. Two of them can correctly match the mRNA so that a
dipeptide can form.
The anticodon loop of the first tRNA that will complement
this mRNA is
A) 3' GGC 5'
B) 5' GGC 3'
C) 5' ACG 3'
D) 5' UGC 3'
E) 3' UGC 5'
Answer: A
71) What type of bonding is responsible for maintaining
the shape of the tRNA molecule?
A) covalent bonding between sulfur atoms
B) ionic bonding between phosphates
C) hydrogen bonding between base pairs
D) van der Waals interactions between hydrogen atoms
E) peptide bonding between amino acids
Answer: C
72) The figure represents tRNA that recognizes and binds
a particular amino acid (in this instance, phenylalanine). Which codon on the
mRNA strand codes for this amino acid?
A) UGG
B) GUG
C) GUA
D) UUC
E) CAU
Answer: D
73) The tRNA shown in the figure has its 3' end
projecting beyond its 5' end. What will occur at this 3' end?
A) The codon and anticodon complement one another.
B) The amino acid binds covalently.
C) The excess nucleotides (ACCA) will be cleaved off at
the ribosome.
D) The small and large subunits of the ribosome will
attach to it.
E) The 5' cap of the mRNA will become covalently bound.
Answer: B
74. The enzyme polynucleotide phosphorylase randomly
assembles nucleotides into a polynucleotide polymer.
You add polynucleotide phosphorylase to a solution of
adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3
nucleotide codons would be possible?
A) 3
B) 4
C) 8
D) 16
E) 64
Answer: C
75. The enzyme polynucleotide phosphorylase randomly
assembles nucleotides into a polynucleotide polymer.
You add polynucleotide phosphorylase to a solution of
ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be
possible?
A) 3
B) 6
C) 9
D) 27
E) 81
Answer: D
76. A transfer RNA (#1) attached to the amino acid lysine
enters the ribosome. The lysine binds to the growing polypeptide on the other
tRNA (#2) in the ribosome already.
Where does tRNA #2 move to after this bonding of lysine
to the polypeptide?
A) A site
B) P site
C) E site
D) exit tunnel
E) directly to the cytosol
Answer: C
77. A transfer RNA (#1) attached to the amino acid lysine
enters the ribosome. The lysine binds to the growing polypeptide on the other
tRNA (#2) in the ribosome already.
Which component of the complex described enters the exit
tunnel through the large subunit of the ribosome?
A) tRNA with attached lysine (#1)
B) tRNA with polypeptide (#2)
C) tRNA that no longer has attached amino acid
D) newly formed polypeptide
E) initiation and elongation factors
Answer: D
78) In eukaryotic cells, transcription cannot begin until
A) the two DNA strands have completely separated and
exposed the promoter.
B) several transcription factors have bound to the
promoter.
C) the 5' caps are removed from the mRNA.
D) the DNA introns are removed from the template.
E) DNA nucleases have isolated the transcription unit.
Answer: B
79) Which of the following is not true of a codon?
A) It consists of three nucleotides.
B) It may code for the same amino acid as another codon.
C) It never codes for more than one amino acid.
D) It extends from one end of a tRNA molecule.
E) It is the basic unit of the genetic code.
Answer: D
80) The anticodon of a particular tRNA molecule is
A) complementary to the corresponding mRNA codon.
B) complementary to the corresponding triplet in rRNA.
C) the part of tRNA that bonds to a specific amino acid.
D) changeable, depending on the amino acid that attaches
to the tRNA.
E) catalytic, making the tRNA a ribozyme.
Answer: A
81) Which of the following is not true of RNA processing?
A) Exons are cut out before mRNA leaves the nucleus.
B) Nucleotides may be added at both ends of the RNA.
C) Ribozymes may function in RNA splicing.
D) RNA splicing can be catalyzed by spliceosomes.
E) A primary transcript is often much longer than the
final RNA molecule that leaves the nucleus.
Answer: A
82) Which component is not directly involved in
translation?
A) mRNA
B) DNA
C) tRNA
D) ribosomes
E) GTP
Answer: B
83) Which of the following mutations would be most likely
to have a harmful effect on an organism?
A) a nucleotide-pair substitution
B) a deletion of three nucleotides near the middle of a
gene
C) a single nucleotide deletion in the middle of an
intron
D) a single nucleotide deletion near the end of the
coding sequence
E) a single nucleotide insertion downstream of, and close
to, the start of the coding sequenceAnswer : E
