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The Dam methylase is responsible for methylating the adenine base in GATC sequences
in Escherichia coli. Imagine two E. coli strains, one without any active Dam methylase,
and the other with a hyperactive version of the enzyme that operates faster than the
wild-type enzyme. Which of these strains would you expect to show a "mutator"
phenotype?
A.Both of the strains
B.Neither of them
C.Only the first strain
D.Only the second strain
Why do cells not have membrane transport proteins for O2?
A.Because they need to keep the oxygen concentration low inside the reducing
environment of the cell.
B.Because oxygen can dissolve in water and leak in via water channels.
C.Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly
without the need for a transporter.
D.Because oxygen is transported in and out of the cell in special oxygen-carrying
proteins such as hemoglobin.
E.Because oxygen transport across a membrane is energetically unfavorable.
Indicate if each of the following structures is based on actin filaments (A), microtubules
(M), or intermediate filaments (I). Your answer would be a five-letter string composed
of letters A, M, and I only; e.g. AAAMM.
( )The cell cortex
( )The mitotic spindle
( )The nuclear lamina
( )Cilia
( )Filopodia
Which of the following proteins is the product of an immediate early gene expressed
following mitogenic stimulation of cell-cycle entry?
A.E2F
B.Rb
C.Myc
D.G1-cyclins
E.All of the above
In the following schematic drawings of aggrecan and decorin, which one (1 or 2)
corresponds to aggrecan? Which one (1 or 2) is synthesized primarily by chondrocytes
in cartilage?
A.1; 1
B.1; 2
C.2; 1
D.2; 2
You have created transgenic mice that carry the gene encoding green fluorescent protein
(GFP) under the control of a ubiquitous promoter. The GFP-encoding gene, however, is
inactive unless recombination by Cre removes a blocking sequence between the
promoter and the gene. These mice have been mated with those harboring the Cre
recombinase under the control of the insulin promoter. The Cre recombinase is fused to
the estrogen receptor, which keeps the fusion in the cytosol unless it binds to tamoxifen,
in which case it allows nuclear entry. After mating, you select adult mice harboring both
of these transgenes and inject them with either tamoxifen or water. Which of the
following would you expect to observe later as a result when you examine brain and
pancreas tissue samples under a fluorescence microscope?
A.GFP signal is observed in the brain in the presence of tamoxifen only.
B.GFP signal is observed in the brain in the absence of tamoxifen only.
C.GFP signal is observed in the pancreas in the presence of tamoxifen only.
D.GFP signal is observed in the pancreas in the absence of tamoxifen only.
E.GFP signal is observed in the brain in either the presence or the absence of tamoxifen.
A benign neoplasia of cartilage is called a ...
A.Chondrocarcinoma
B.Chondroma
C.Chondrosarcoma
D.Adenochondroma
E.Chondromelanoma
An axonal growth cone has reached a muscle fiber and is forming a neuromuscular
junction. Which of the following events does NOT normally occur in this process?
A.Agrin secreted from the growth cone serves as a signaling molecule affecting the
muscle cell.
B.LRP4 on the surface of the growth cone serves as a signaling molecule affecting the
muscle cell.
C.Synaptic vesicles containing the neurotransmitter acetylcholine appear in the growth
cone.
D.Acetylcholine receptors cluster on the muscle cell plasma membrane at the junction.
E.A thin layer of basal lamina forms at the cleft between the two cell membranes at the
junction.
What two cell-surface receptors are represented in the two simplified diagrams below
(from left to right)?
A.TGF receptor and TNF receptor.
B.Cytokine receptor and TNF receptor.
C.TNF receptor and TGF receptor.
D.TGF receptor and cytokine receptor.
E.Cytokine receptor and TGF receptor.
Indicate whether each of the following occurs inside the cell in the presence (P) or
absence (A) of stimulation with a Hedgehog signal. Your answer would be a four-letter
string composed of letters P and A only, e.g. PPPP.
( )Sequestration of Smoothened in intracellular vesicles
( )Accumulation of unprocessed Ci in the nucleus
( )Phosphorylation of Smoothened
( )Recruitment of Fused and Costal2 to the plasma membrane
In Gram staining, crystal violet (a violet dye) is used to specifically stain Gram-positive
bacteria. After performing Gram staining on a bacterial sample taken from an infected
animal tissue, you observe the results with a microscope. You find two major types of
bacteria in the sample, as shown in the schematic drawing below. According to these
results, indicate whether each of the following statements is correct (C) or incorrect (I).
Your answer would be a three-letter string composed of letters C and I only, e.g. CCC.
( )The Gram-positive bacteria in this sample are bacilli.
( )Crystal violet stains lipopolysaccharide (LPS).
( )The bacteria stained violet in this sample have a thicker layer of peptidoglycan
compared to the other bacteria.
Which of the following transporters is NOT electrogenic?
A.Na+-glucose symporter
B.Ca2+-pump
C.Na+-K+ pump
D.Na+-independent Cl--HCO3
- exchanger
E.Bacteriorhodopsin
Imagine a protein that has been engineered to contain a nuclear localization signal, a
nuclear export signal, a C-terminal peroxisomal targeting sequence, and a canonical
endoplasmic reticulum (ER) signal sequence. With all of these signals, where would
you expect to find the protein after its synthesis?
A.Cytosol
B.Nucleus
C.Shuttling between the cytosol and the nucleus
D.Peroxisomes
E.Endoplasmic reticulum
In a developing Drosophila melanogaster embryo, a hierarchy of gene regulatory
interactions subdivides the embryo to regulate progressively finer details of patterning.
For each of the following proteins, indicate which expression pattern (1 to 4) in the
schematic drawing below is more appropriate. Your answer would be a four-digit
number composed of digits 1 to 4 only, with each digit used once, e.g. 3412.
( )Hunchback (product of a gap gene)
( )Engrailed (product of a segment-polarity gene)
( )Bicoid (product of an egg-polarity gene)
( )Even-skipped (product of a pair-rule gene)
Indicate whether each of the following descriptions better applies to bacterial (B),
fungal (F), protozoan (P), or viral (V) pathogens. Your answer would be a four-letter
string composed of letters B, F, P, and V only, e.g. FFFB.
( )They cannot be all grouped neatly into a single phylogenetic tree.
( )They have the most complex life cycles.
( )They are essentially fragments of nucleic acid wrapped in a protective shell of
proteins and (in some cases) an outer membrane.
( )They are responsible for diseases such as polio and smallpox.
Some signaling pathways in the cell are chiefly based on inhibition rather than
activation. For example, proteins that initiate programmed cell death by apoptosis are
inhibited by anti-apoptotic proteins, which can in turn be inhibited by a group of
pro-apoptotic proteins, and so on. Consider the following networks of inhibitory
interactions, in which each protein is inactive if at least one of its inhibitors is active. In
which pathway is the activation of either upstream protein (1 or 2) sufficient to inhibit
apoptosis?
A schematic drawing of the secretory and endocytic pathways is presented below.
Indicate which component in the drawing (A to J) corresponds to each of the following.
Your answer would be a 10-letter string composed of letters A to J only, e.g.
HICDJABFGE.
( )Early endosome
( )Late endosome
( )ER
( )Lysosome
( )cis Golgi cisterna
( )medial Golgi cisterna
( )trans Golgi cisterna
( )cis Golgi network (CGN)
( )trans Golgi network (TGN)
( )Secretory vesicle
Indicate true (T) and false (F) statements below regarding the complement system. Your
answer would be a four-letter string composed of letters T and F only, e.g. TTFT.
( )The early complement components form the membrane attack complex, whereas the
late complement components cleave and activate C3.
( )The classical pathway of complement activation is triggered by binding of a secreted
PRR to mannose-containing glycoproteins or glycolipids on the surface of pathogens.
( )Some pathogens such as Neisseria gonorrhoeae hide from the complement reaction
via sialic acid camouflage.
( )Once a membrane attack complex is formed, it can attack multiple pathogens before
becoming inactivated.
Indicate whether each of the following descriptions better applies to SIM (S), STED
(T), or STORM/PALM (P) superresolution techniques. Your answer would be a
four-letter string composed of letters S, T, and P only, e.g. PPTS.
( )It switches on and off individual fluorophores at random over time to accurately
determine their position.
( )It creates a moire pattern from the interference of the illuminating pattern and the
sample features.
( )It doubles the resolution of conventional fluorescence microscopy.
( )It limits excitation to the fluorophores that are located at the center of the focal point
by using a doughnut-shaped beam in addition to the excitation beam.
Indicate true (T) and false (F) statements below regarding fatty acid metabolism. Your
answer would be a four-letter string composed of letters T and F only, e.g. TTTT.
( )Most animals derive their energy from fatty acids between meals.
( )Fatty acids are converted to acetyl CoA in the cytosol, which is then transported into
mitochondria for further oxidation.
( )Fatty acids are stored in fat droplets in the form of triacylglycerols.
( )The breakdown of fatty acids into each acetyl CoA unit requires the hydrolysis of two
ATP molecules.
