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14
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.
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.
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.
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
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
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
Art Questions
Use the following information to answer the following questions.
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.
Drosophila embryo after about 2 hours.
59) 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.
60) 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.
61) 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.
62) 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.
63) 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.
Scenario Questions
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences
within a prokaryotic genome.
64) 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.
65) 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.
66) 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.
67) 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.
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.
68) 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.
69) 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
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation
in embryonic cells in culture.
70) 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
71) 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
72) 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
73) 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
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.
74) 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.
75) 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
76) 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.
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.
77) 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.
78) 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.
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):
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.
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.
80) 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
81) 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.
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.
82) 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
83) 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
84) 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.
85) 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.
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.
86) 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.
87) 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.
88) 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.
89) 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.
End-of-Chapter Questions
The following questions are from the end-of-chapter “Test Your Understanding” section in Chapter 18
of the textbook.
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.
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.
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.
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.
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
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)
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.
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.
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.
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.
