What do all -barrel transmembrane proteins have in common?
A.The number of strands.
B.The diameter of the barrel.
C.The number of negative peaks in their hydropathy plots.
D.The general function, i.e. membrane transport.
E.The structural rigidity compared to -helical transmembrane proteins.
To trace family relationships between distantly related organisms such as humans,
algae, bacteria, and archaea, one should compare their genomes in regions ___
A.that evolve rapidly.
B.that have a higher mutation rate.
C.that code for proteins.
D.where mutations are hardly tolerated.
E.where most mutations are selectively neutral.
The electron carriers NADH and FADH2 donate their electrons to the electron-transport
chain in the inner mitochondrial membrane, leading to ATP synthesis powered by an H+
gradient across the membrane. If, on average, the oxidation of each NADH or FADH2
molecule in this pathway results in the production of 2.5 and 1.5 molecules of ATP,
respectively, how many ATP (and GTP) molecules are produced on average as a result
of the complete oxidation of one molecule of acetyl CoA in the mitochondrion?
Consider only the citric acid cycle and oxidative phosphorylation.
A.10
B.12
C.13.5
D.14.5
E.15
The SCF ubiquitin ligase can recognize and mark various target proteins at different
stages of the cell cycle. In this complex, ___
A.different F-box subunits recognize different target proteins.
B.the F-box subunit and the E2 ubiquitin-conjugating enzyme are at the opposite ends
of the C-shaped molecule.
C.a scaffold protein arranges the other subunits such that the two ends of the complex
are separated by a gap.
D.the use of interchangeable parts such as the F-box subunits makes economical use of
the genetic information and allows for rapid evolution of new functions.
E.All of the above.
How is the organization of epithelial cells in epidermis different from that in the lining
of the intestine?
A.The epidermis is stratified and squamous (i.e. forms squames).
B.The stem-cell niche in epidermis is provided by the basal lamina and the underlying
connective tissue.
C.The transit amplifying cells in the epidermis move mostly perpendicular to the plane
of the epithelium.
D.The cells of the epidermis die long before they are shed.
E.All of the above.
The following simplified diagram shows the typical sequence of genetic changes in a
developing colorectal carcinoma. Indicate which event (A to C) corresponds to the
following changes. Your answer would be a three-letter string composed of letters A to
C only, e.g. CAB.
( )Activation of K-Ras
( )Loss of p53
( )Loss of Apc
Although quite inefficient, cloning by nuclear transplantation can be successful, as
exemplified by cloning of the famous Dolly. Such a success implies that …
A.nuclei can be reprogrammed by cytoplasmic factors in a foreign cytoplasm.
B.epigenetic changes in somatic cells are not functionally irreversible.
C.even a differentiated nucleus contains a complete genome, capable of supporting the
development of an entire organism.
D.All of the above.
The following graph shows the change in the concentration of a protein (A) over time
as a fraction of the final steady-state level. The two curves (1 and 2) in the graph are
simulations with similar parameters except that one of them involves a negative
feedback loop in which A activates the expression of a repressor protein which in turn
represses the expression of A. Which curve (1 or 2) corresponds to the simulation with
the negative feedback loop? Write down 1 or 2 as your answer.
The chromatin remodeling complexes play an important role in chromatin regulation in
the nucleus. They ___
A.can slide nucleosomes on DNA.
B.have ATPase activity.
C.interact with histone chaperones.
D.can remove or exchange core histone subunits.
E.All of the above.
In the following simplified diagram of the NFºB-dependent signaling pathway, indicate
which boxes (A to C) correspond to the NF-ºB, IºB, and IKK proteins, respectively.
Your answer would be a three-letter string composed of letters A to C only, e.g. BCA.
Which of the following is true regarding Escherichia coli?
A.Most of our understanding about mitosis comes from studies on this model organism.
B.It is a rod-shaped bacterium that can only grow in the gut of humans and other
vertebrates.
C.Two strains of E. coli can differ by up to 0.1% in their genomes.
D.E. coli strain K-12 encodes about 4300 proteins.
E.The E. coli (strain K-12) genome is about 430 million nucleotide pairs long.
Which of the following correctly summarizes the overall process of photosynthesis?
A.CO2 + O2 –> H2O + sugars
B.CH2O + CO2 + O2 –> H2O + sugars
C.CO2 + H2O –> H2 + CO2
D.CO2 + H2O –> O2 + sugars
A patient with persisting larger-than-normal lymph nodes is suspected to have a T cell
lymphoma, a cancer of T lymphocytes. Abnormally enlarged lymph nodes are also
found in local infections, when lymphocytes are activated to proliferate there. In order
to distinguish between cancer and infection, you take tissue samples from the patient, as
well as from a healthy individual, and perform a so-called clonality test. You extract
DNA from the tissues and amplify a small chromosomal region that includes the
T-cell-receptor chain D-J junctions. Amplification is done by PCR, using primers
that hybridize to specific DNA sequences flanking the junctions. You then analyze the
size distributions of the PCR products by capillary electrophoresis, which makes it
possible to distinguish between DNA molecules with small differences in size. Based
on the results, presented in the following schematic graphs, you conclude that,
unfortunately, it is likely that the patient has developed a T cell lymphoma. Which
graph (1 or 2) represents the patient’s test results? Write down 1 or 2 as your answer.
You have used “optical tweezers” to study the mechanics of myosin movement in a
newly discovered member of the myosin II subfamily. Your results indicate that each
myosin exerts a force of about 3 pN along the length of the actin filament, and displaces
the filament by about 10 nm in each cycle of ATP hydrolysis. Assuming that the
free-energy change for ATP hydrolysis is -50 kJ/mol under your experimental
conditions, what is the efficiency of the myosin motor in converting the free energy to
mechanical work? Remember that under a constant force F (in newtons), work (W; in
joules) is calculated as W = F x d, where d is displacement (in meters) in the direction
of the force. Avogadro’s number is approximately 6 x 1023 molecules/mole. Write down
your answer as a percentage with no decimals, e.g. 99%.
The following schematic drawing represents the activation of transcription for a
eukaryotic gene (gene X). Indicate what component (A to D) in the drawing
corresponds to each of the following. Your answer would be a four-letter string
composed of letters A to D only, e.g. ADBC.
( )Mediator
( )cis-Regulatory sequence
( )A general transcription factor
( )”Spacer” DNA that may encode lncRNAs
Indicate whether each of the following descriptions better applies to the determination
of atomic structure of proteins by x-ray diffraction (X) or by nuclear magnetic
resonance (NMR) spectroscopy (N). Your answer would be a five-letter string
composed of letters X and N only, e.g. NNXNN.
( )It is more suitable for complexes larger than about 100 kD.
( )It requires samples to crystallize.
( )It can better reveal dynamics of molecular motions.
( )It involves the calculation of electron-density maps.
( )It is used to determine the solution structure of proteins.
Indicate true (T) and false (F) statements below regarding erythropoiesis. Your answer
would be a four-letter string composed of letters T and F only, e.g. TTTF.
( )Oxygen stimulates the secretion of erythropoietin.
( )Each human erythrocyte lives for a few days on average.
( )All erythrocytes express “DON’T EAT ME” signals on their surface to prevent
phagocytosis.
( )It only takes 1 to 2 days for erythrocyte numbers to rise following stimulation with
erythropoietin.
In a forensic lab, DNA samples from a mother (M) and her child (C) have been
analyzed at three short tandem repeat (STR) loci using PCR and gel electrophoresis.
The same analysis has been performed for five men (1 to 5). According to the results
below, which men can be eliminated as possible candidates for the biological father of
the child? Your answer would be a number composed of digits 1 to 5 only, e.g. 145
In the following schematic diagram of a typical eukaryotic cell cycle, choose two major
time points (among A to E) at which the cell-cycle control system normally arrests the
cycle if DNA damage is detected. Your answer would be a two-letter string composed
of letters A to E only in alphabetical order, e.g. CE.
Indicate whether each of the following processes is topologically similar (Y) or not
similar (N) to formation of intralumenal vesicles in multivesicular bodies. Your answer
would be a four-letter string composed of letters Y and N only, e.g. YYYY.
( )Fission of peroxisomes
( )Formation of clathrin-coated vesicles
( )Budding of HIV from infected cells
( )Cytokinesis