1) The role of a metabolite that controls a repressible
operon is to
A) bind to the promoter region and decrease the affinity
of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment
of RNA polymerase to the promoter.
C) increase the production of inactive repressor
proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it.
Answer: E
2) The tryptophan operon is a repressible operon that is
A) permanently turned on.
B) turned on only when tryptophan is present in the
growth medium.
C) turned off only when glucose is present in the growth
medium.
D) turned on only when glucose is present in the growth
medium.
E) turned off whenever tryptophan is added to the growth
medium.
Answer: E
3) Which of the following is a protein produced by a
regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor
E) corepressor
Answer: D
4) A lack of which molecule would result in the cell's
inability to "turn off" genes?
A) operon
B) inducer
C) promoter
D) ubiquitin
E) corepressor
Answer: E
5) Which of the following, when taken up by the cell,
binds to the repressor so that the repressor no longer binds to the operator?
A) ubiquitin
B) inducer
C) promoter
D) repressor
E) corepressor
Answer: B
6) Most repressor proteins are allosteric. Which of the
following binds with the repressor to alter its conformation?
A) inducer
B) promoter
C) RNA polymerase
D) transcription factor
E) cAMP
Answer: A
7) A mutation that inactivates the regulatory gene of a
repressible operon in an E. coli cell would result in
A) continuous transcription of the structural gene
controlled by that regulator.
B) complete inhibition of transcription of the structural
gene controlled by that regulator.
C) irreversible binding of the repressor to the operator.
D) inactivation of RNA polymerase by alteration of its
active site.
E) continuous translation of the mRNA because of
alteration of its structure.
Answer: A
8) The lactose operon is likely to be transcribed when
A) there is more glucose in the cell than lactose.
B) the cyclic AMP levels are low.
C) there is glucose but no lactose in the cell.
D) the cyclic AMP and lactose levels are both high within
the cell.
E) the cAMP level is high and the lactose level is low.
Answer: D
9) Transcription of the structural genes in an inducible
operon
A) occurs continuously in the cell.
B) starts when the pathway's substrate is present.
C) starts when the pathway's product is present.
D) stops when the pathway's product is present.
E) does not result in the production of enzymes.
Answer: B
10) For a repressible operon to be transcribed, which of
the following 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 cannot be present, and the repressor
must be inactive.
E) RNA polymerase must not occupy the promoter, and the
repressor must be inactive.
Answer: C
11) Allolactose, an isomer of lactose, is formed in small
amounts from lactose. An E. coli cell is presented for the first time with the
sugar lactose (containing allolactose) as a potential food source. Which of the
following occurs when the lactose enters the cell?
A) The repressor protein attaches to the regulator.
B) Allolactose binds to the repressor protein.
C) Allolactose binds to the regulator gene.
D) The repressor protein and allolactose bind to RNA
polymerase.
E) RNA polymerase attaches to the regulator.
Answer: B
12) Altering patterns of gene expression in prokaryotes
would most likely serve the organism's survival in which of the following ways?
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 the organism to adjust to changes in
environmental conditions
D) allowing young organisms to respond differently from
more mature organisms
E) allowing environmental changes to alter the prokaryote's
genome
Answer: C
13) In response to chemical signals, prokaryotes can do
which of the following?
A) turn off translation of their mRNA
B) alter the level of production of various enzymes
C) increase the number and responsiveness of their ribosomes
D) inactivate their mRNA molecules
E) alter the sequence of amino acids in certain proteins
Answer: B
14) If glucose is available in the environment of E.
coli, the cell responds with a very low concentration of cAMP. When the cAMP
increases in concentration, it binds to CAP. Which of the following would you
expect to be a measurable effect?
A) decreased concentration of the lac enzymes
B) increased concentration of the trp enzymes
C) decreased binding of the RNA polymerase to sugar
metabolism-related promoters
D) decreased concentration of alternative sugars in the
cell
E) increased concentrations of sugars such as arabinose
in the cell
Answer: E
15) In positive control of several
sugar-metabolism-related operons, the catabolite activator protein (CAP) binds
to DNA to stimulate transcription. What causes an increase in CAP?
A) increase in glucose and increase in cAMP
B) decrease in glucose and increase in cAMP
C) increase in glucose and decrease in cAMP
D) decrease in glucose and increase in repressor
E) decrease in glucose and decrease in repressor
Answer: B
16) There is a mutation in the repressor that results in
a molecule known as a super-repressor because it represses the lac operon
permanently. Which of these would characterize such a mutant?
A) It cannot bind to the operator.
B) It cannot make a functional repressor.
C) It cannot bind to the inducer.
D) It makes molecules that bind to one another.
E) It makes a repressor that binds CAP.
Answer: C
17) Which of the following mechanisms is (are) used to
coordinate the expression of multiple, related genes in eukaryotic cells?
A) Genes are organized into clusters, with local chromatin
structures influencing the expression of all the genes at once.
B) The genes share a common intragenic sequence, and
allow several activators to turn on their transcription, regardless of
location.
C) The genes are organized into large operons, allowing
them to be transcribed as a single unit.
D) A single repressor is able to turn off several related
genes.
E) Environmental signals enter the cell and bind directly
to promoters.
Answer: A
18) If you were to observe the activity of methylated
DNA, you would expect it to
A) be replicating nearly continuously.
B) be unwinding in preparation for protein synthesis.
C) have turned off or slowed down the process of
transcription.
D) be very actively transcribed and translated.
E) induce protein synthesis by not allowing repressors to
bind to it.
Answer: C
19) Genomic imprinting, DNA methylation, and histone
acetylation are all examples of
A) genetic mutation.
B) chromosomal rearrangements.
C) karyotypes.
D) epigenetic phenomena.
E) translocation.
Answer: D
20) When DNA is compacted by histones into 10-nm and
30-nm fibers, the DNA is unable to interact with proteins required for gene
expression. Therefore, to allow for these proteins to act, the chromatin must
constantly alter its structure. Which processes contribute to this dynamic
activity?
A) DNA supercoiling at or around H1
B) methylation and phosphorylation of histone tails
C) hydrolysis of DNA molecules where they are wrapped
around the nucleosome core
D) accessibility of heterochromatin to phosphorylating
enzymes
E) nucleotide excision and reconstruction
Answer: B
21) Two potential devices that eukaryotic cells use to
regulate transcription are
A) DNA methylation and histone amplification.
B) DNA amplification and histone methylation.
C) DNA acetylation and methylation.
D) DNA methylation and histone modification.
E) histone amplification and DNA acetylation.
Answer: D
22) During DNA replication,
A) all methylation of the DNA is lost at the first round
of replication.
B) DNA polymerase is blocked by methyl groups, and
methylated regions of the genome are therefore left uncopied.
C) methylation of the DNA is maintained because
methylation enzymes act at DNA sites where one strand is already methylated and
thus correctly methylates daughter strands after replication.
D) methylation of the DNA is maintained because DNA
polymerase directly incorporates methylated nucleotides into the new strand
opposite any methylated nucleotides in the template.
E) methylated DNA is copied in the cytoplasm, and
unmethylated DNA is copied in the nucleus.
Answer: C
23) In eukaryotes, general transcription factors
A) are required for the expression of specific protein-encoding
genes.
B) bind to other proteins or to a sequence element within
the promoter called the TATA box.
C) inhibit RNA polymerase binding to the promoter and
begin transcribing.
D) usually lead to a high level of transcription even
without additional specific transcription factors.
E) bind to sequences just after the start site of
transcription.
Answer: B
24) Steroid hormones produce their effects in cells by
A) activating key enzymes in metabolic pathways.
B) activating translation of certain mRNAs.
C) promoting the degradation of specific mRNAs.
D) binding to intracellular receptors and promoting
transcription of specific genes.
E) promoting the formation of looped domains in certain
regions of DNA.
Answer: D
25) Transcription factors in eukaryotes usually have DNA
binding domains as well as other domains that are also specific for binding. In
general, which of the following would you expect many of them to be able to
bind?
A) repressors
B) ATP
C) protein-based hormones
D) other transcription factors
E) tRNA
Answer: D
26) Gene expression might be altered at the level of
post-transcriptional processing in eukaryotes rather than prokaryotes because
of which of the following?
A) Eukaryotic mRNAs get 5' caps and 3' tails.
B) Prokaryotic genes are expressed as mRNA, which is more
stable in the cell.
C) Eukaryotic exons may be spliced in alternative
patterns.
D) Prokaryotes use ribosomes of different structure and
size.
E) Eukaryotic coded polypeptides often require cleaving
of signal sequences before localization.
Answer: C
27) Which of the following experimental procedures is
most likely to hasten mRNA degradation in a eukaryotic cell?
A) enzymatic shortening of the poly-A tail
B) removal of the 5' cap
C) methylation of C nucleotides
D) methylation of histones
E) removal of one or more exons
Answer: B
28) Which of the following is most likely to have a small
protein called ubiquitin attached to it?
A) a cyclin that usually acts in G₁, now that the cell is
in G₂
B) a cell surface protein that requires transport from
the ER
C) an mRNA that is leaving the nucleus to be translated
D) a regulatory protein that requires sugar residues to
be attached
E) an mRNA produced by an egg cell that will be retained
until after fertilization
Answer: A
29) In prophase I of meiosis in female Drosophila,
studies have shown that there is phosphorylation of an amino acid in the tails
of histones of gametes. A mutation in flies that interferes with this process
results in sterility. Which of the following is the most likely hypothesis?
A) These oocytes have no histones.
B) Any mutation during oogenesis results in sterility.
C) All proteins in the cell must be phosphorylated.
D) Histone tail phosphorylation prohibits chromosome
condensation.
E) Histone tails must be removed from the rest of the
histones.
Answer: D
30) The phenomenon in which RNA molecules in a cell are
destroyed if they have a sequence complementary to an introduced
double-stranded RNA is called
A) RNA interference.
B) RNA obstruction.
C) RNA blocking.
D) RNA targeting.
E) RNA disposal.
Answer: A
31) At the beginning of this century there was a general
announcement regarding the sequencing of the human genome and the genomes of
many other multicellular eukaryotes. There was surprise expressed by many that
the number of protein-coding sequences was much smaller than they had expected.
Which of the following could account for most of the rest?
A) "junk" DNA that serves no possible purpose
B) rRNA and tRNA coding sequences
C) DNA that is translated directly without being
transcribed
D) non-protein-coding DNA that is transcribed into
several kinds of small RNAs with biological function
E) non-protein-coding DNA that is transcribed into
several kinds of small RNAs without biological function
Answer: D
32) Among the newly discovered small noncoding RNAs, one
type reestablishes methylation patterns during gamete formation and block
expression of some transposons. These are known as
A) miRNA.
B) piRNA.
C) snRNA.
D) siRNA.
E) RNAi.
Answer: B
33) Which of the following best describes siRNA?
A) a short double-stranded RNA, one of whose strands can
complement and inactivate a sequence of mRNA
B) a single-stranded RNA that can, where it has internal
complementary base pairs, fold into cloverleaf patterns
C) a double-stranded RNA that is formed by cleavage of
hairpin loops in a larger precursor
D) a portion of rRNA that allows it to bind to several
ribosomal proteins in forming large or small subunits
E) a molecule, known as Dicer, that can degrade other
mRNA sequences
Answer: A
34) One way scientists hope to use the recent knowledge
gained about noncoding RNAs lies with the possibilities for their use in
medicine. Of the following scenarios for future research, which would you
expect to gain most from RNAs?
A) exploring a way to turn on the expression of
pseudogenes
B) targeting siRNAs to disable the expression of an
allele associated with autosomal recessive disease
C) targeting siRNAs to disable the expression of an
allele associated with autosomal dominant disease
D) creating knock-out organisms that can be useful for
pharmaceutical drug design
E) looking for a way to prevent viral DNA from causing
infection in humans
Answer: C
35) Which of the following describes the function of an
enzyme known as Dicer?
A) It degrades single-stranded DNA.
B) It degrades single-stranded mRNA.
C) It degrades mRNA with no poly-A tail.
D) It trims small double-stranded RNAs into molecules
that can block translation.
E) It chops up single-stranded DNAs from infecting
viruses.
Answer: D
36) In a series of experiments, the enzyme Dicer has been
inactivated in cells from various vertebrates so that the centromere is
abnormally formed from chromatin. Which of the following is most likely to
occur?
A) The usual mRNAs transcribed from centromeric DNA will
be missing from the cells.
B) Tetrads will no longer be able to form during meiosis
I.
C) Centromeres will be euchromatic rather than
heterochromatic and the cells will soon die in culture.
D) The cells will no longer be able to resist bacterial
contamination.
E) The DNA of the centromeres will no longer be able to
replicate.
Answer: C
37) Since Watson and Crick described DNA in 1953, which
of the following might best explain why the function of small RNAs is still
being explained?
A) As RNAs have evolved since that time, they have taken
on new functions.
B) Watson and Crick described DNA but did not predict any
function for RNA.
C) The functions of small RNAs could not be approached
until the entire human genome was sequenced.
D) Ethical considerations prevented scientists from
exploring this material until recently.
E) Changes in technology as well as our ability to
determine how much of the DNA is expressed have now made this possible.
Answer: E
38) You are given an experimental problem involving
control of a gene's expression in the embryo of a particular species. One of
your first questions is whether the gene's expression is controlled at the
level of transcription or translation. Which of the following might best give
you an answer?
A) You explore whether there has been alternative
splicing by examining amino acid sequences of very similar proteins.
B) You measure the quantity of the appropriate pre-mRNA
in various cell types and find they are all the same.
C) You assess the position and sequence of the promoter
and enhancer for this gene.
D) An analysis of amino acid production by the cell shows
you that there is an increase at this stage of embryonic life.
E) You use an antibiotic known to prevent translation.
Answer: B
39) In humans, the embryonic and fetal forms of
hemoglobin have a higher affinity for oxygen than that of adults. This is due
to
A) nonidentical genes that produce different versions of
globins during development.
B) identical genes that generate many copies of the
ribosomes needed for fetal globin production.
C) pseudogenes, which interfere with gene expression in
adults.
D) the attachment of methyl groups to cytosine following
birth, which changes the type of hemoglobin produced.
E) histone proteins changing shape during embryonic
development.
Answer: A
40) The fact that plants can be cloned from somatic cells
demonstrates that
A) differentiated cells retain all the genes of the
zygote.
B) genes are lost during differentiation.
C) the differentiated state is normally very unstable.
D) differentiated cells contain masked mRNA.
E) differentiation does not occur in plants.
Answer: A
41) In animals, embryonic stem cells differ from adult
stem cells in that
A) embryonic stem cells are totipotent, and adult stem
cells are pluripotent.
B) embryonic stem cells are pluripotent, and adult stem
cells are totipotent.
C) embryonic stem cells have more genes than adult stem
cells.
D) embryonic stem cells have fewer genes than adult stem
cells.
E) embryonic stem cells are localized to specific sites
within the embryo, whereas adult stem cells are spread throughout the body.
Answer: A
42) What is considered to be the first evidence of
differentiation in the cells of an embryo?
A) cell division occurring after fertilization
B) the occurrence of mRNAs for the production of
tissue-specific proteins
C) determination of specific cells for certain functions
D) changes in the size and shape of the cell
E) changes resulting from induction
Answer: B
43) Embryonic lethal mutations result in
A) phenotypes that prevent fertilization.
B) failure to express maternal effect genes.
C) death during pupation.
D) phenotypes that are never born/hatched.
E) homeotic phenotype changes.
Answer: D
44) Your brother has just purchased a new plastic model
airplane. He places all the parts on the table in approximately the positions
in which they will be located when the model is complete. His actions are
analogous to which process in development?
A) morphogenesis
B) determination
C) induction
D) differentiation
E) pattern formation
Answer: E
45) The product of the bicoid gene in Drosophila provides
essential information about
A) lethal genes.
B) the dorsal-ventral axis.
C) the left-right axis.
D) segmentation.
E) the anterior-posterior axis.
Answer: E
46) If a Drosophila female has a homozygous mutation for
a maternal effect gene,
A) she will not develop past the early embryonic stage.
B) all of her offspring will show the mutant phenotype,
regardless of their genotype.
C) only her male offspring will show the mutant
phenotype.
D) her offspring will show the mutant phenotype only if
they are also homozygous for the mutation.
E) only her female offspring will show the mutant
phenotype.
Answer: B
47) Mutations in which of the following genes lead to
transformations in the identity of entire body parts?
A) morphogens
B) segmentation genes
C) egg-polarity genes
D) homeotic genes
E) inducers
Answer: D
48) Which of the following genes map out the basic
subdivisions along the anterior-posterior axis of the Drosophila embryo?
A) homeotic genes
B) segmentation genes
C) egg-polarity genes
D) morphogens
E) inducers
Answer: B
49) Gap genes and pair-rule genes fall into which of the
following categories?
A) homeotic genes
B) segmentation genes
C) egg-polarity genes
D) morphogens
E) inducers
Answer: B
50) The bicoid gene product is normally localized to the
anterior end of the embryo. If large amounts of the product were injected into
the posterior end as well, which of the following would occur?
A) The embryo would grow to an unusually large size.
B) The embryo would grow extra wings and legs.
C) The embryo would probably show no anterior development
and die.
D) Anterior structures would form in both sides of the
embryo.
E) The embryo would develop normally.
Answer: D
51) What do gap genes, pair-rule genes, segment polarity
genes, and homeotic genes all have in common?
A) Their products act as transcription factors.
B) They have no counterparts in animals other than
Drosophila.
C) Their products are all synthesized prior to
fertilization.
D) They act independently of other positional
information.
E) They apparently can be activated and inactivated at
any time of the fly's life.
Answer: A
52) Which of the following statements describes
proto-oncogenes?
A) Their normal function is to suppress tumor growth.
B) They are introduced to a cell initially by
retroviruses.
C) They are produced by somatic mutations induced by
carcinogenic substances.
D) They can code for proteins associated with cell
growth.
E) They are underexpressed in cancer cells.
Answer: D
53) Which of the following is characteristic of the
product of the p53 gene?
A) It is an activator for other genes.
B) It speeds up the cell cycle.
C) It causes cell death via apoptosis.
D) It allows cells to pass on mutations due to DNA
damage.
E) It slows down the rate of DNA replication by
interfering with the binding of DNA polymerase.
Answer: A
54) Tumor-suppressor genes
A) are frequently overexpressed in cancerous cells.
B) are cancer-causing genes introduced into cells by
viruses.
C) can encode proteins that promote DNA repair or
cell-cell adhesion.
D) often encode proteins that stimulate the cell cycle.
E) do all of the above.
Answer: C
55) BRCA1 and BRCA2 are considered to be tumor-suppressor
genes because
A) they prevent infection by retroviruses that cause
cancer.
B) their normal products participate in repair of DNA
damage.
C) the mutant forms of either one of these promote breast
cancer.
D) the normal genes make estrogen receptors.
E) they block penetration of breast cells by chemical
carcinogens.
Answer: B
56) The cancer-causing forms of the Ras protein are
involved in which of the following processes?
A) relaying a signal from a growth factor receptor
B) DNA replication
C) DNA repair
D) cell-cell adhesion
E) cell division
Answer: A
57) Forms of the Ras protein found in tumors usually
cause which of the following?
A) DNA replication to stop
B) DNA replication to be hyperactive
C) cell-to-cell adhesion to be nonfunctional
D) cell division to cease
E) growth factor signaling to be hyperactive
Answer: E
58) A genetic test to detect predisposition to cancer
would likely examine the APC gene for involvement in which type(s) of cancer?
A) colorectal only
B) lung and breast
C) small intestinal and esophageal
D) lung only
E) lung and prostate
Answer: A
59. In Drosophila after ~100 minutes postfertilization, the
embryo looks like the following diagram, with all nuclei having moved to the
periphery and, subsequently, four of the nuclei being sequestered at the
posterior end
.
At this point, the embryo is characterized as
A) a first-stage larva.
B) nuclei in the cortex that has not undergone
cytokinesis.
C) nuclei in the cortex forming a single-cell layer over
the surface.
D) an embryo with segmentation beginning to be apparent.
Answer: B
60. In Drosophila after ~100 minutes postfertilization, the
embryo looks like the following diagram, with all nuclei having moved to the
periphery and, subsequently, four of the nuclei being sequestered at the
posterior end.
The four sequestered cells at one end are most
probably destined to become
A) the legs of the adult fly.
B) the germ cells of the adult.
C) mouthparts.
D) antennae.
E) wing primordial.
Answer: B
61. In Drosophila after ~100 minutes postfertilization, the
embryo looks like the following diagram, with all nuclei having moved to the
periphery and, subsequently, four of the nuclei being sequestered at the
posterior end.
Formation of the pole cells (the four sequestered
cells) demonstrates the role of
A) segmentation genes.
B) homeotic genes.
C) maternal effect genes.
D) zygotic genes.
E) all of the above.
Answer: C
62. In Drosophila after ~100 minutes postfertilization, the
embryo looks like the following diagram, with all nuclei having moved to the
periphery and, subsequently, four of the nuclei being sequestered at the
posterior end.
The next step after the embryo is formed would be
A) division of the embryo into five broad regions.
B) use of pair-rule genes to divide the embryo into
stripes, each of which will become two segments.
C) use of zygotic segment polarity genes to divide each
segment into anterior and posterior halves.
D) enclosure of the nuclei in membranes, forming a single
layer over the surface.
E) separation of head, thoracic, and abdominal segments
of the embryo.
Answer: D
63. In Drosophila after ~100 minutes postfertilization, the
embryo looks like the following diagram, with all nuclei having moved to the
periphery and, subsequently, four of the nuclei being sequestered at the
posterior end.
The developmental stages described for Drosophila
illustrate
A) a hierarchy of gene expression.
B) homeotic developmental control.
C) the blockage of cell-to-cell communication.
D) homeotic developmental control and the blockage of
cell-to-cell communication.
E) a hierarchy of gene expression and the blockage of
cell-to-cell communication.
Answer: A
64. Suppose an experimenter becomes proficient with a
technique that allows her to move DNA sequences within a prokaryotic genome
If she moves the promoter for the lac operon to the
region between the beta galactosidase gene and the permease gene, which of the
following would be likely?
A) Three structural genes will no longer be expressed.
B) RNA polymerase will no longer transcribe permease.
C) The operon will no longer be inducible.
D) Beta galactosidase will be produced.
E) The cell will continue to metabolize but more slowly.
Answer: D
65. Suppose an experimenter becomes proficient with a
technique that allows her to move DNA sequences within a prokaryotic genome
If she moves the operator to the far end of the
operon (past the transacetylase gene), which of the following 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 structural genes will be transcribed continuously.
E) The repressor protein will no longer be produced.
Answer: D
66. Suppose an experimenter becomes proficient with a
technique that allows her to move DNA sequences within a prokaryotic genome
If she moves the repressor gene (lac I), along with
its promoter, to a position at some several thousand base pairs away from its
normal position, which will you expect to occur?
A) The repressor will no longer be made.
B) The repressor will no longer bind to the operator.
C) The repressor will no longer bind to the inducer.
D) The lac operon will be expressed continuously.
E) The lac operon will function normally.
Answer: E
67. Suppose an experimenter becomes proficient with a
technique that allows her to move DNA sequences within a prokaryotic genome
If she moves the operator to a position upstream from
the promoter, what would occur?
A) The lac operon will function normally.
B) The lac operon will be expressed continuously.
C) The repressor will not be able to bind to the
operator.
D) The repressor will bind to the promoter.
E) The repressor will no longer be made.
Answer: B
68. A geneticist introduces a transgene into yeast cells and
isolates five independent cell lines in which the transgene has integrated into
the yeast genome. In four of the lines, the transgene is expressed strongly,
but in the fifth there is no expression at all.
Which of the following is a likely explanation for
the lack of transgene expression in the fifth cell line?
A) A transgene integrated into a heterochromatic region
of the genome.
B) A transgene integrated into a euchromatic region of
the genome.
C) The transgene was mutated during the process of
integration into the host cell genome.
D) The host cell lacks the enzymes necessary to express
the transgene.
E) A transgene integrated into a region of the genome
characterized by high histone acetylation.
Answer: A
69. A geneticist introduces a transgene into yeast cells and
isolates five independent cell lines in which the transgene has integrated into
the yeast genome. In four of the lines, the transgene is expressed strongly,
but in the fifth there is no expression at all.
Of the lines that express the transgene, one is
transcribed but not translated. Which of the following is a likely explanation?
A) no promoter
B) no AUG in any frame
C) no compatible ribosome
D) high histone acetylation
E) missing transcription factor
Answer: B
70. A researcher found a method she could use to manipulate
and quantify phosphorylation and methylation in embryonic cells in culture.
In one set of experiments using this procedure in
Drosophila, she was readily successful in increasing phosphorylation of amino
acids adjacent to methylated amino acids in histone tails. Which of the
following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes
Answer: B
71. A researcher found a method she could use to manipulate
and quantify phosphorylation and methylation in embryonic cells in culture.
In one set of experiments she succeeded in decreasing
methylation of histone tails. Which of the following results would she most
likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes
Answer: A
72. A researcher found a method she could use to manipulate
and quantify phosphorylation and methylation in embryonic cells in culture.
One of her colleagues suggested she try increased
methylation of C nucleotides in a mammalian system. Which of the following
results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes
Answer: E
73. A researcher found a method she could use to manipulate
and quantify phosphorylation and methylation in embryonic cells in culture.
She tried decreasing the amount of methylation
enzymes in the embryonic stem cells and then allowed the cells to further
differentiate. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes
Answer: C
74. A researcher introduces double-stranded RNA into a
culture of mammalian cells, and can identify its location or that of its
smaller subsections experimentally, using a fluorescent probe.
Within the first quarter hour, the researcher sees
that the intact RNA is found in the cells. After 3 hours, she is not surprised
to find that
A) Dicer enzyme has reduced it to smaller double-stranded
pieces.
B) the RNA is degraded by 5' and 3' exonucleases.
C) the double-stranded RNA replicates itself.
D) the double-stranded RNA binds to mRNAs to prevent
translation.
E) the double-stranded RNA binds to tRNAs to prevent translation.
Answer: A
75. A researcher introduces double-stranded RNA into a
culture of mammalian cells, and can identify its location or that of its
smaller subsections experimentally, using a fluorescent probe.
Some time later, she finds that the introduced strand
separates into single-stranded RNAs, one of which is degraded. What does this
enable the remaining strand to do?
A) attach to histones in the chromatin
B) bind to complementary regions of target mRNAs
C) bind to Dicer enzymes to destroy other RNAs
D) activate other siRNAs in the cell
E) bind to noncomplementary RNA sequences
Answer: B
76. A researcher introduces double-stranded RNA into a
culture of mammalian cells, and can identify its location or that of its
smaller subsections experimentally, using a fluorescent probe.
In addition, she finds what other evidence of this
single-stranded RNA piece's activity?
A) She can measure the degradation rate of the remaining
single strand.
B) She can measure the decrease in the concentration of
Dicer.
C) The rate of accumulation of the polypeptide to be
translated from the target mRNA is reduced.
D) The amount of miRNA is multiplied by its replication.
E) The cell's translation ability is entirely shut down.
Answer: C
77. A researcher has arrived at a method to prevent gene
expression from Drosophila embryonic genes. The following questions assume that
he is using this method.
The researcher in question measures the amount of new
polypeptide production in embryos from 2—8 hours following fertilization and
the results show a steady and significant rise in polypeptide concentration
over that time. The researcher concludes that
A) his measurement skills must be faulty.
B) the results are due to building new cell membranes to
compartmentalize dividing nuclei.
C) the resulting new polypeptides are due to translation
of maternal mRNAs.
D) the new polypeptides were inactive and not measurable
until fertilization.
E) polypeptides were attached to egg membranes until this
time.
Answer: C
78. A researcher has arrived at a method to prevent gene
expression from Drosophila embryonic genes. The following questions assume that
he is using this method.
The researcher continues to study the reactions of
the embryo to these new proteins and you hypothesize that he is most likely to
see which of the following (while embryonic genes are still not being
expressed)?
A) The cells begin to differentiate.
B) The proteins are evenly distributed throughout the
embryo.
C) Larval features begin to make their appearance.
D) Spatial axes (anterior → posterior, etc.) begin to be
determined.
E) The embryo begins to lose cells due to apoptosis from
no further gene expression.
Answer: D
79. The researcher measures the concentration of the
polypeptides from different regions in the early embryo and finds the following
pattern (darker shading = greater concentration): SEE IMAGE
Which of the following would be his most logical
assumption?
A) The substance has moved quickly from region 5 to
region 1.
B) Some other material in the embryo is causing
accumulation in region 1 due to differential binding.
C) The cytosol is in constant movement, dispersing the
polypeptide.
D) The substance is produced in region 1 and diffuses
toward region 5.
E) The substance must have entered the embryo from the
environment near region 1.
Answer: D
80. One hereditary disease in humans, called xeroderma
pigmentosum (XP), makes homozygous individuals exceptionally susceptible to
UV-induced mutation damage in the cells of exposed tissue, especially skin.
Without extraordinary avoidance of sunlight exposure, patients soon succumb to
numerous skin cancers.
Which of the following best describes this
phenomenon?
A) inherited cancer taking a few years to be expressed
B) embryonic or fetal cancer
C) inherited predisposition to mutation
D) inherited inability to repair UV-induced mutation
E) susceptibility to chemical carcinogens
Answer: D
81. One hereditary disease in humans, called xeroderma
pigmentosum (XP), makes homozygous individuals exceptionally susceptible to
UV-induced mutation damage in the cells of exposed tissue, especially skin.
Without extraordinary avoidance of sunlight exposure, patients soon succumb to
numerous skin cancers.
Given the damage caused by UV, the kind of gene
affected in those with XP is one whose product is involved with
A) mending of double-strand breaks in the DNA backbone.
B) breakage of cross-strand covalent bonds.
C) the ability to excise single-strand damage and replace
it.
D) the removal of double-strand damaged areas.
E) causing affected skin cells to undergo apoptosis.
Answer: C
82. A few decades ago, Knudsen and colleagues proposed a
theory that, for a normal cell to become a cancer cell, a minimum of two
genetic changes had to occur in that cell. Knudsen was studying retinoblastoma,
a childhood cancer of the eye.
Two children are born from the same parents. Child
one inherits a predisposition to retinoblastoma (one of the mutations) and
child two does not. However, both children develop the retinoblastoma. Which of
the following would you expect?
A) an earlier age of onset in child one
B) a history of exposure to mutagens in child one but not
in child two
C) a more severe cancer in child one
D) increased levels of apoptosis in both children
E) decreased levels of DNA repair in child one
Answer: A
83. A few decades ago, Knudsen and colleagues proposed a
theory that, for a normal cell to become a cancer cell, a minimum of two
genetic changes had to occur in that cell. Knudsen was studying retinoblastoma,
a childhood cancer of the eye.
In colorectal cancer, several genes must be mutated
in order to make a cell a cancer cell, supporting Knudsen's hypothesis. Which
of the following kinds of genes would you expect to be mutated?
A) genes coding for enzymes that act in the colon
B) genes involved in control of the cell cycle
C) genes that are especially susceptible to mutation
D) the same genes that Knudsen identified as associated
with retinoblastoma
E) the genes of the bacteria that are abundant in the
colon
Answer: B
84. A few decades ago, Knudsen and colleagues proposed a
theory that, for a normal cell to become a cancer cell, a minimum of two
genetic changes had to occur in that cell. Knudsen was studying retinoblastoma,
a childhood cancer of the eye.
Knudsen and colleagues also noted that persons with
hereditary retinoblastoma that had been treated successfully lived on but then
had a higher frequency of developing osteosarcomas (bone cancers) later in
life. This provided further evidence of their theory because
A) osteosarcoma cells express the same genes as retinal
cells.
B) p53 gene mutations are common to both tumors.
C) both kinds of cancer involve overproliferation of
cells.
D) one of the mutations involved in retinoblastoma is
also one of the changes involved in osteosarcoma.
E) retinoblastoma is a prerequisite for the formation of
osteosarcoma later in life.
Answer: D
85. A few decades ago, Knudsen and colleagues proposed a
theory that, for a normal cell to become a cancer cell, a minimum of two
genetic changes had to occur in that cell. Knudsen was studying retinoblastoma,
a childhood cancer of the eye.
One of the human leukemias, called CML (chronic
myelogenous leukemia), is associated with a chromosomal translocation between
chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following
allows CML to provide further evidence of this multistep nature of cancer?
A) CML usually occurs in more elderly persons (late age
of onset).
B) The resulting chromosome 22 is abnormally short; it is
then known as the Philadelphia chromosome.
C) The translocation requires breaks in both chromosomes
9 and 22, followed by fusion between the reciprocal pieces.
D) CML involves a proto-oncogene known as abl.
E) CML can usually be treated by chemotherapy.
Answer: C
86. Epstein Bar Virus (EBV) causes most of us to have an
episode of sore throat and swollen glands during early childhood. If we first
become exposed to the virus during our teen years, however, EBV causes the
syndrome we know as mononucleosis. However, in special circumstances, the same
virus can be carcinogenic.
In areas of the world in which malaria is endemic,
notably in sub-Saharan Africa, EBV can cause Burkitt's lymphoma in children,
which is usually associated with large tumors of the jaw. Which of the
following is consistent with these findings?
A) EBV infection makes the malarial parasite able to
produce lymphoma.
B) Malaria's strain on the immune system makes EBV
infection worse.
C) Malaria occurs more frequently in those infected with
EBV.
D) Malarial response of the immune system prevents an
individual from making EBV antibodies.
E) A cell infected with the malarial parasite is more
resistant to the virus.
Answer: D
87. Epstein Bar Virus (EBV) causes most of us to have an
episode of sore throat and swollen glands during early childhood. If we first
become exposed to the virus during our teen years, however, EBV causes the
syndrome we know as mononucleosis. However, in special circumstances, the same
virus can be carcinogenic.
In a different part of the world, namely in parts of
southeast Asia, the same virus is associated with a different kind of cancer of
the throat. Which of the following is most probable?
A) Viral infection is correlated with a different
immunological reaction.
B) The virus infects the people via different routes.
C) The virus only infects the elderly.
D) The virus mutates more frequently in the Asian
population.
E) Malaria is also found in this region.
Answer: A
88. Epstein Bar Virus (EBV) causes most of us to have an
episode of sore throat and swollen glands during early childhood. If we first
become exposed to the virus during our teen years, however, EBV causes the
syndrome we know as mononucleosis. However, in special circumstances, the same
virus can be carcinogenic.
A very rare human allele of a gene called XLP, or
X-linked lymphoproliferative syndrome, causes a small number of people from
many different parts of the world to get cancer following even childhood
exposure to EBV. Given the previous information, what might be going on?
A) The people must have previously had malaria.
B) Their ancestors must be from sub-Saharan Africa or
southeast Asia.
C) They must be unable to mount an immune response to
EBV.
D) They must have severe combined immune deficiency
(SCID).
E) Their whole immune system must be overreplicating.
Answer: C
89. Epstein Bar Virus (EBV) causes most of us to have an
episode of sore throat and swollen glands during early childhood. If we first
become exposed to the virus during our teen years, however, EBV causes the
syndrome we know as mononucleosis. However, in special circumstances, the same
virus can be carcinogenic.
What must characterize the XLP population?
A) They must have severe immunological problems starting
at birth.
B) They must all be males with affected male relatives.
C) They must all be males with affected female relatives.
D) They must all inherit this syndrome from their
fathers.
E) They must live in sub-Saharan Africa.
Answer: C
90). If a particular operon encodes enzymes for making an
essential amino acid and is regulated like the trp operon, then
A) the amino acid inactivates the repressor.
B) the enzymes produced are called inducible enzymes.
C) the repressor is active in the absence of the amino
acid.
D) the amino acid acts as a corepressor.
E) the amino acid turns on transcription of the operon.
Answer: D
91) Muscle cells differ from nerve cells mainly because
they
A) express different genes.
B) contain different genes.
C) use different genetic codes.
D) have unique ribosomes.
E) have different chromosomes.
Answer: A
92) The functioning of enhancers is an example of
A) transcriptional control of gene expression.
B) a post-transcriptional mechanism to regulate mRNA.
C) the stimulation of translation by initiation factors.
D) post-translational control that activates certain
proteins.
E) a eukaryotic equivalent of prokaryotic promoter
functioning.
Answer: A
93) Cell differentiation always involves
A) the production of tissue-specific proteins, such as
muscle actin.
B) the movement of cells.
C) the transcription of the myoD gene.
D) the selective loss of certain genes from the genome.
E) the cell's sensitivity to environmental cues, such as
light or heat.
Answer: A
94) Which of the following is an example of
post-transcriptional control of gene expression?
A) the addition of methyl groups to cytosine bases of DNA
B) the binding of transcription factors to a promoter
C) the removal of introns and alternative splicing of
exons
D) gene amplification contributing to cancer
E) the folding of DNA to form heterochromatin
Answer: C
95) What would occur if the repressor of an inducible
operon were mutated so it could not bind the operator?
A) irreversible binding of the repressor to the promoter
B) reduced transcription of the operon's genes
C) buildup of a substrate for the pathway controlled by
the operon
D) continuous transcription of the operon's genes
E) overproduction of catabolite activator protein (CAP)
Answer: D
96) Absence of bicoid mRNA from a Drosophila egg leads to
the absence of anterior larval body parts and mirror-image duplication of
posterior parts. This is evidence that the product of the bicoid gene
A) is transcribed in the early embryo.
B) normally leads to formation of tail structures.
C) normally leads to formation of head structures.
D) is a protein present in all head structures.
E) leads to programmed cell death.
Answer: C
97) Which of the following statements about the DNA in
one of your brain cells is true?
A) Most of the DNA codes for protein.
B) The majority of genes are likely to be transcribed.
C) Each gene lies immediately adjacent to an enhancer.
D) Many genes are grouped into operon-like clusters.
E) It is the same as the DNA in one of your heart cells.
Answer: E
98) Within a cell, the amount of protein made using a
given mRNA molecule depends partly on
A) the degree of DNA methylation.
B) the rate at which the mRNA is degraded.
C) the presence of certain transcription factors.
D) the number of introns present in the mRNA.
E) the types of ribosomes present in the cytoplasm.
Answer: B
99) Proto-oncogenes can change into oncogenes that cause
cancer. Which of the following best explains the presence of these potential
time bombs in eukaryotic cells?
A) Proto-oncogenes first arose from viral infections.
B) Proto-oncogenes normally help regulate cell division.
C) Proto-oncogenes are genetic "junk."
D) Proto-oncogenes are mutant versions of normal genes.
E) Cells produce proto-oncogenes as they age.
Answer: B
