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Type IV collagen molecules can interact at their C-termini to form dimers and at their
N-termini to form tetramers. What category do you think this type of collagen belongs
to?
A.Fibrillar
B.Fibril-associated
C.Network-forming
D.Proteoglycan core
E.Anchorage fibril
Carcinoma of the uterine cervix in humans ...
A.can be largely prevented by vaccination.
B.is caused by a retrovirus.
C.is caused by activation of a viral Src kinase.
D.rapidly progresses (from uterine warts) to malignancy.
E.All of the above.
The substrate for the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase is
glyceraldehyde 3-phosphate (with one phosphate group) while its product is
1,3-bisphosphoglycerate (with two phosphate groups). Where does the extra phosphate
group come from?
A.From combining two molecules of the substrate
B.ATP
C.Fructose 1,6-bisphosphate
D.Pi
E.NADH
To create cellular factories for monoclonal antibody production, cells derived from an
immortalized B lymphocyte cell line (M) are cultured together with antibody-secreting
B lymphocytes (B) on a so-called HAT medium. The medium contains an inhibitor of
DHFR, an enzyme essential for de novo nucleotide biosynthesis. Additionally, it
contains substrates for the only alternative nucleotide biosynthetic pathway called the
salvage pathway. The enzyme HGPRT is essential for the salvage pathway. One of the
cells mentioned above lacks the gene encoding one of the enzymes mentioned.
Considering the role of the HAT medium in selecting for hybrid cells that are both
immortalized and secrete antibodies, which cell (B or M) do you think is missing an
enzyme? Which enzyme is missing in this cell?
A.M - DHFR
B.M - HGPRT
C.B - DHFR
D.B - HGPRT
The schematic drawing below shows the cross section of a crypt in the gut epithelium
of a mammal. Indicate whether each of the following descriptions better applies to the
areas labeled A, B, or C. Your answer would be a four-letter string composed of letters
A to C only, e.g. CCBB.
( )The stem cells reside in this area.
( )This area contains the most rapidly dividing cells.
( )Cells in this area would show the least radioactivity following a pulse of tritiated
thymidine.
( )This area contains cells of the innate immune system.
The binding of protein A to two other proteins, B and C, has been studied with
fluorescence anisotropy, and the results of the measurements have been plotted in the
following schematic diagram. Given equal kon rate constants, which complex do you
think has a longer half-life? What is the value of Ka (the association constant) for this
complex?
A.A-B; 105 L/mol
B.A-B; 10-5 L/mol
C.A-C; 1.5 x 105 L/mol
D.A-C; 6.7 x 104 L/mol
E.A-C; 6.7 x 10-4 L/mol
Which subset of the following is directly involved in driving protein import into the
mitochondrial matrix space? Choose all correct sources. Your answer would be a string
composed of letters A to G only, in alphabetical order, e.g. AE.
A.ATP hydrolysis inside mitochondria
B.ATP hydrolysis outside mitochondria
C.GTP hydrolysis inside mitochondria
D.GTP hydrolysis outside mitochondria
E.Light
F.Membrane potential across the inner membrane
G.Membrane potential across the outer membrane
Which components of the extracellular matrix are mostly responsible for its ability to
resist compressive and tensile forces, respectively?
A.Collagens and glycoproteins
B.Glycoproteins and collagens
C.Glycosaminoglycans and glycoproteins
D.Glycosaminoglycans and collagens
E.Collagens and glycosaminoglycans
Reconstitution of vesicle transport in cell-free systems was historically carried out in
the presence of isolated "donor" and "acceptor" Golgi stacks. The donor stacks are
isolated from cells expressing a viral protein and lacking a processing enzyme. The
protein can be transported to the acceptor stacks (that do contain the processing
enzyme) and be processed only in the presence of an energy source (such as ATP) and a
cytosolic fraction. The transport vesicles that mediate this process are visualized by
microscopy. Various compounds can be added to this system to help understand the
mechanism of transport. Two such compounds were added in early experiments in the
1980s, both of which blocked transport of the viral protein and resulted in the
accumulation of transport vesicles. However, the accumulated vesicles following
treatment with one of these compounds (A) appeared to be coated, while those resulting
from treatment with the other compound (B) did not. If one of these compounds is a
nonhydrolyzable GTP analog and the other one is N-ethylmaleimide, which compound
(A or B) do you think represents the GTP analog? Write down A or B as your answer.
The molecules inside the cell constantly collide with other molecules and diffuse
through the cytoplasm in a random walk. The average net distance traveled by such a
molecule after a certain time period t is proportional to the square root of t, i.e. (t)0.5, as
well as to its diffusion coefficient. If, on average, it takes a molecule 100 milliseconds
to travel a net distance of 0.5 µm from its starting point, how long would it normally
take for the same molecule to travel a net distance of 5 µm from the same starting
point?
A.0.2 second
B.0.3 second
C.1 second
D.10 seconds
E.0.32 seconds
What is the major microtubule-organizing center in animal cells?
A.The -tubulin ring complex
B.The centrosome
C.The cell cortex
D.The primary cilium
E.The spindle pole body
Where do individual peptides get fragmented in a tandem mass spectrometry (MS/MS)
set-up?
A.Electrospray ion source
B.Mass filter
C.Inert gas chamber
D.Mass analyzer
E.Detector
Compared to the cytosol, which of the following is generally true about the lumen of
the endoplasmic reticulum in our cells?
A.It has a higher pH.
B.It has a more reducing environment.
C.It has a much higher calcium ion concentration.
D.It has a higher density of ribosomes.
E.All of the above.
Laboratory strains of the model organism Escherichia coli that are resistant to
antibiotics are very often used in research laboratories as well as in the biotechnology
industry. If cultures of such bacteria were allowed to contaminate the environment
uncontrollably, it is possible that at some point, pathogenic bacteria such as Neisseria
meningitidis (which causes meningitis and can cause death, especially in children)
could acquire the same antibiotic-resistance gene, causing a meningitis outbreak that is
difficult to treat. In this scenario, which of the following mechanisms is a more likely
source of the antibiotic-resistance gene in N. meningitidis?
A.Random new gene generation
B.Intragenic mutation
C.Gene duplication
D.DNA segment shuffling
E.Horizontal gene transfer
Consider a biochemical pathway in petal cells of a plant, in which a white precursor is
turned into a final red pigment through a yellow and an orange intermediate by the
activity of three enzymes encoded by genes A, B, and C. The petal color in plants
harboring functional (capital letter) or nonfunctional (lowercase letter) alleles of these
genes is presented in the following table. What do you think is the order in which the
enzymes act in the pathway? Your answer would be a three-letter string composed of
letters A to C, e.g. BCA.
Indicate whether each of the following descriptions matches actin filaments (A),
microtubules (M), or intermediate filaments (I). Your answer would be a three-letter
string composed of letters A, M, and I only, e.g. MMA.
( )They have the smallest persistence length.
( )They lack polarity.
( )They have the highest tensile strength.
Which of the following is correct regarding neuronal self-avoidance in both
invertebrates and vertebrates?
A.They both rely on alternative splicing to generate the diversity required to uniquely
identify each neuron.
B.They both result in tiling, in which not more than one neuron occupies a certain
territory.
C.They both rely on protocadherins.
D.They both use a strategy in which homophilic recognition results in avoidance.
E.All of the above.
In medical oncology, PET (positron emission tomography) is used to selectively image
tumors in the body and to monitor cancer progression and response to treatment. Before
performing a PET scan, the patient should fast for at least several hours for blood
glucose to be sufficiently low. At the time of the scan, the positron-emitting glucose
analog fluorodeoxyglucose (FDG) is injected into the bloodstream and the patient is
asked to wait for up to an hour while avoiding physical activity. Finally, the scanner
moves slowly over the body to reveal the location of possible tumors. Why do you think
the patient should avoid physical activity before the scan?
A.To prevent the Warburg effect
B.To accelerate glucose uptake by the tumor cells
C.To prevent the absorption of the radioactive tracer by healthy tissues
D.To promote fermentation in healthy tissues
E.All of the above
Which of the following proteins lacks a PH domain?
A.Sos (a Ras-GEF)
B.Grb2 (an RTK signaling adaptor)
C.Pleckstrin (a protein kinase C substrate)
D.Akt (protein kinase B)
E.PDK1 (phosphoinositide-dependent kinase)
Reference: Contractile-Ring Positioning
Three models for contractile-ring positioning in animal cells are presented in the
schematic diagrams below. Answer the following question(s) according to these models.
In the early embryos of Caenorhabditis elegans, defects in the formation of astral
microtubules increase myosin activity throughout the cell cortex. If the spindle is forced
to one side of the cell, the cortical myosin activity is observed mostly at the opposite
side of the cell. Which model (1, 2, or 3) better predicts these observations? Write down
1, 2, or 3 as your answer.
In the highly simplified diagram below, the energy landscape of secretory vesicle fusion
to the plasma membrane is shown in the presence or absence of appropriate SNARE
complexes. Which curve (A or B) do you think corresponds to the presence of SNARE
complexes? Write down A or B as your answer.
In the bacterium Yersinia pestis, which causes bubonic plague, loss of an operon that is
normally responsible for iron storage diminishes the ability of the cells to form biofilms
and colonize inside the iron-rich gut of infected fleas. Would you expect the efficiency
of transmission of plague to increase (I), decrease (D), or remain unchanged (U) as a
result of this mutation? Write down I, D, or U as your answer.
Indicate true (T) and false (F) statements below regarding glycosylation of proteins in
the endoplasmic reticulum and the Golgi apparatus. Your answer would be a four-letter
string composed of letters T and F only, e.g. TTTF
( )Glycosylation can promote protein folding.
( )The glycosylation state of a protein can determine its fate along the secretory
pathway.
( )Glycosylation makes a protein more accessible to proteases and other proteins.
( )Glycosylated proteins are generally more flexible.
Indicate whether each of the following viruses is mostly associated with cervical cancer
(C), Kaposi's sarcoma (K), liver cancer (L), or stomach cancer (S). Your answer would
be a four-letter string composed of letters C, K, L, and S, e.g. CKLS.
( )Hepatitis-B virus (HBV)
( )Human immunodeficiency virus (HIV)
( )Human papillomavirus (HPV)
( )Helicobacter pylori
Indicate true (T) and false (F) statements below regarding signaling in plants. Your
answer would be a four-letter string composed of letters T and F only, e.g. TTTF.
( )Since multicellularity evolved before the divergence of the plant and animal lineages,
plants have homologs of most animal signaling proteins, such as nuclear receptors, Ras,
JAK, and Notch.
( )Receptor tyrosine kinases are the largest class of cell-surface receptors in plant cells.
( )Both plants and animals use cyclic GMP, NO, and Ca2+ for cell signaling.
( )Leucine-rich repeat (LLR) receptor kinases are the most abundant type of receptor
serine/threonine kinases in plants.
In contrast to vertebrates, there is very little DNA methylation in the genomes of
invertebrates such as Drosophila melanogaster and Caenorhabditis elegans. Indicate
whether you expect each of the following statements to be true (T) or false (F)
regarding 5'-CG-3' dinucleotide sequences in the genome. Your answer would be a
four-letter string composed of letters T and F only, e.g. TTTT.
( )On average, approximately one dinucleotide out of every 16 in the human genome is
a CG dinucleotide.
( )On average, approximately one dinucleotide out of every 256 in the D.melanogaster
genome is a CG dinucleotide.
( )The proportion of CG dinucleotides in the human genome is more than that of C.
elegans.
( )The proportion of CG dinucleotides in the human genome is more than that expected
by chance.
Which of the following transporters mediates primary active transport when
transporting the solutes in the directions indicated? The concentration of both solutes
(shown as small circles and squares) is higher outside of the cell.
Which strand in an miRNA precursor will serve as the guide strand in the RNA-induced
silencing complex (RISC)? Analysis of miRNA sequences has revealed an asymmetry
in the stability of the double-stranded RNA precursor. The strand showing lower
thermodynamic stability near its 5' end (nucleotides 2 to 6 in the mature guide strand) is
normally selected as the guide strand, and the other strand is usually degraded. In the
following miRNA precursor, which strand (1 or 2) do you think will be incorporated
into the active RISC? Write down 1 or 2 as your answer.
