front 5 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 | |
front 6 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 | |
front 7 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. | |
front 8 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. | |
front 9 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. | |
front 10 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. | |
front 11 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. | |
front 12 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 | |
front 13 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 | |
front 14 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 | |
front 15 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 | |
front 16 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. | |
front 17 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. | |
front 18 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. | |
front 19 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. | |
front 20 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 | |
front 21 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. | |
front 22 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. | |
front 23 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. | |
front 24 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. | |
front 25 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 | |
front 26 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. | |
front 27 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 | |
front 28 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 Gā, now that the cell is in Gā
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 | |
front 29 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. | |
front 30 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. | |
front 31 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 | |
front 32 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. | |
front 33 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 | |
front 34 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 | |
front 35 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. | |
front 36 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. | |
front 37 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. | |
front 38 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. | |
front 39 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. | |
front 40 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. | |
front 41 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. | |
front 42 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 | |
front 43 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. | |
front 44 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 | |
front 45 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. | |
front 46 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. | |
front 47 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 | |
front 48 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 | |
front 49 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 | |
front 50 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. | |
front 51 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. | |
front 52 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. | |
front 53 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. | |
front 54 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. | |
front 55 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. | |
front 56 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 | |
front 57 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 | |
front 58 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 | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 64 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. | |
front 65 Suppose an experimenter becomes proficient with a technique that
allows her to move DNA sequences within a prokaryotic genome
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. | |
front 66 Suppose an experimenter becomes proficient with a technique that
allows her to move DNA sequences within a prokaryotic genome
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. | |
front 67 Suppose an experimenter becomes proficient with a technique that
allows her to move DNA sequences within a prokaryotic genome
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. | |
front 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.
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. | |
front 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.
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 | |
front 70 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 | |
front 71 A researcher found a method she could use to manipulate and quantify
phosphorylation and methylation in embryonic cells in culture.
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 | |
front 72 A researcher found a method she could use to manipulate and quantify
phosphorylation and methylation in embryonic cells in culture.
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 | |
front 73 A researcher found a method she could use to manipulate and quantify
phosphorylation and methylation in embryonic cells in culture.
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 | |
front 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.
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. | |
front 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.
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 | |
front 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.
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. | |
front 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.
77) The researcher in question measures the amount of new
polypeptide production in embryos from 2ā8 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. | |
front 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.
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 ā posterior, etc.) begin to be determined.
E) The embryo begins to lose cells due to apoptosis from no
further gene expression. | |
front 79 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. | |
front 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.
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 | |
front 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.
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. | |
front 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.
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 | |
front 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.
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 | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 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.
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. | |
front 90 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. | |
front 91 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. | |
front 92 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. | |
front 93 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. | |
front 94 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 | |
front 95 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) | |
front 96 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. | |
front 97 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. | |
front 98 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. | |
front 99 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. | |