Chromosome 3 contains nearly 200 million nucleotide pairs of our genome. If this DNA
molecule could be laid end to end, how long would it be? The distance between
neighboring base pairs in DNA is typically around 0.34 nm.
A.About 7 mm
B.About 7 cm
C.About 70 cm
D.About 7 m
E.None of the above
RNA-seq and ribosome profiling experiments have been carried out on the same cells.
The following simplified graphs show the results for the same genomic region
containing a gene with three exons. Which graph (1 or 2) do you think corresponds to
the RNA-seq results? What feature is represented by the arrow?
A.Graph 1; stop codon
B.Graph 1; polyadenylation site
C.Graph 2; stop codon
D.Graph 2; polyadenylation site
Mycobacterium tuberculosis can cause tuberculosis, a life-threatening lung infection,
but can also infect an individual asymptomatically for years. It is not considered to be
part of the normal flora, and can infect healthy individuals upon exposure. It can only
replicate in the host and thus mainly spreads by direct human contact. Mycobacterium
tuberculosis is therefore €¦
A.a facultative primary pathogen.
B.a facultative opportunistic pathogen.
C.an obligate primary pathogen.
D.an obligate opportunistic pathogen.
Stem cells can be obtained from self-renewing regions of an adult vertebrate brain,
cultured in suspension or in monolayer, and later grafted back into a live animal. When
implanted, stem cells isolated from mouse hippocampus …
A.can only give rise to hippocampus neurons, even in a different location in the brain.
B.can give rise to neurons in another part of the brain, e.g. in the olfactory bulb.
C.are unable to proliferate unless implanted in the hippocampus, where they contribute
to its neurons.
D.can give rise to any cell (e.g. muscle cells) when implanted into muscle tissue.
The acetylation of lysines on the histone tails ___
A.loosens the chromatin structure because it adds positive charges to the histone.
B.recruits the heterochromatin protein HP1, resulting in the establishment of
heterochromatin.
C.can be performed on methylated lysines only after they are first demethylated.
D.is sufficient for the formation of an open chromatin structure.
E.is a covalent modification and is thus irreversible.
Which of the regulatory interactions 1 to 5 depicted in the following diagram is NOT an
example of a negative feedback regulation?
A.1
B.2
C.3
D.4
E.5
In the presence of an ATP analog that can bind myosin normally but cannot be
hydrolyzed, …
A.a myosin cannot bind tightly to an actin filament and cannot move on it.
B.a myosin cannot be released from an actin filament and cannot move on it.
C.a myosin performs the power stroke but cannot be released from an actin filament.
D.a myosin performs the power stroke but cannot bind tightly to an actin filament.
E.a myosin is able to perform normally.
Cytochalasin D (CyD) is a drug that binds to the plus end of actin filaments and
prevents actin polymerization. Having identified mutations in actin that confer
resistance to CyD, a researcher sets out to study the role of the actin cytoskeleton in the
invasion of mammalian host cells by two intracellular parasites: the protozoan
Toxoplasma gondii and the bacterium Salmonella enterica. She infects wild-type or
CyD-resistant host cells with either wild-type T. gondii, CyD-resistant T. gondii, or
wild-type S. enterica, each in the presence (+) or absence (-) of CyD, and measures
parasite internalization and intracellular proliferation as a result. The findings are
summarized in the table below, in which High or Low levels of proliferation are
indicated. According to these results, which column (A to C) do you think corresponds
to infection with wild-type T. gondii? Which column corresponds to CyD-resistant T.
gondii? Which row (D or E) corresponds to the wild-type host? Your answer would be a
three-letter string composed of letters A to E only, e.g. ABE.
What combination of the following events normally prevents the origins of replication
in the yeast Saccharomyces cerevisiae from “firing” more than once during the cell
cycle? Your answer is a two-letter string composed of letters A to E only, e.g. AB. Order
the letters in your answer alphabetically.
(A)The helicase-loading proteins Cdc6 and Cdt1 are only active in S phase.
(B)The helicase Mcm1 can be delivered to the origin recognition complex (ORC) only
in S phase.
(C)The ORC can only become active (by dephosphorylation) in G1 phase.
(D)The helicase can only become active (by phosphorylation) in S phase.
(E)The ORC can bind to the origin only in S phase.
A small unique insert found near the end of the motor domain in myosin VI has been
linked to the singular ability of this myosin to move toward the pointed end of actin
filaments. If the unique insert is removed by genetic engineering, the resulting mutant
myosin VI is a plus-end directed motor. This observation indicates that …
A.the unique insert is necessary and sufficient for minus-end directionality.
B.the unique insert is necessary for motor activity.
C.the unique insert is necessary for plus-end directed directionality.
D.the unique insert is not sufficient for minus-end directionality.
E.None of the above.
How is membrane protrusion by blebbing different from that by lamellipodia?
A.Blebbing usually occurs on a rigid substratum such as glass, whereas lamellipodia
form on pliable substrata.
B.Blebbing is mostly observed in vitro, whereas lamellipodia are observed both in vitro
and in vivo.
C.Blebbing does not involve myosin II activity, but formation of lamellipodia does.
D.Blebbing requires loss of membrane interaction with actin filaments, whereas
lamellipodia require a close interaction between the two.
E.All of the above.
Indicate if each of the following changes occurring during mitosis in a fibroblast is the
result of the reorganization of 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. AIAAM.
( )The cell rounds up.
( )The endoplasmic reticulum collapses.
( )The Golgi apparatus fragments.
( )The primary cilium is resorbed (disappears).
( )The contractile ring forms and constricts.
Indicate whether each of the following descriptions better applies to the cisternal
maturation model (C) or the vesicle transport model (V) for the organization of the
Golgi apparatus. Your answer would be a four-letter string composed of letters C and V
only, e.g. CVCV.
( )Golgi cisternae are static organelles.
( )Golgi cisternae exchange material exclusively by retrograde vesicular transport.
( )A cis Golgi cisterna becomes a medial cisterna which becomes a trans cisterna.
( )Any protein that passes through the Golgi apparatus should be incorporated into
transport vesicles several times.
Which of the following would you NOT expect to find in a bacterial cell?
A.Swimming using flagella
B.Having a cell wall around the plasma membrane
C.ATP production in mitochondria
D.Protein production on the ribosome
E.Sexual exchange of DNA with other bacteria
Sort the following events in a sequence that would lead to long-term potentiation (LTP).
Your answer would be a five-digit number composed of numbers 1 to 5 only, e.g.
13245.
(A)Activation of AMPA receptors
(B)Glutamate release into the synaptic clefts
(C)Activation of calcium-dependent protein kinases in the postsynaptic cell
(D)Postsynaptic membrane depolarization
(E)Activation of NMDA receptors
A cell has been subjected to ultraviolet irradiation, causing a significant number of
mutations in the genome. Which of the following would you NOT expect to occur as a
result?
A.Activation of the protein kinase ATR
B.Activation of the protein kinase Chk1
C.Inactivation of the protein phosphatase Cdc25
D.Binding of p53 to Mdm2
E.Stabilization of p53
Indicate whether each of the following descriptions better applies to phytochromes (P),
cryptochromes (C), or phototropins (T). Your answer would be a four-letter string
composed of letters P, C, and T only, e.g. TPCC.
( )They respond to red light.
( )They are found in animals as well as in plants.
( )They are flavoproteins.
( )They are dimeric, cytosolic serine/threonine protein kinases that are normally
activated by autophosphorylation.
Indicate true (T) and false (F) statements below regarding the RNA world hypothesis.
Your answer would be a four-letter string composed of letters T and F only, e.g. TFFF.
( )According to this hypothesis, RNA in primitive cells was responsible for storing
genetic information, while proteins were responsible for the catalysis of chemical
reactions.
( )The existence of natural ribozymes supports this hypothesis.
( )In support of this hypothesis, all peptides in present-day cells are made by the
ribosome.
( )All present-day cells use DNA as their hereditary material.
Indicate true (T) and false (F) statements below regarding the pattern of cell
proliferation in the epithelium that forms the lining of the small intestine. Your answer
would be a four-letter string composed of letters T and F only, e.g. TTTT.
( )New epithelial cells are constantly born throughout the epithelial sheet, mostly at the
villi.
( )Every type of intestinal epithelial cell is eventually discarded into the gut lumen
where they die.
( )There is a net movement of cells from the bottom of the crypts up toward the tip of
the villi.
( )The majority of intestinal epithelial cells have packed microvilli on their apical
surfaces.
Indicate whether each of the following descriptions better applies to mitogens (M),
growth factors (G), or survival factors (S). Your answer would be a four-letter string
composed of letters M, G, or S only, e.g. GMSG.
( )They unblock cell-cycle progression
( )They suppress apoptosis
( )They trigger a wave of G1/S-Cdk activity
( )They inhibit the degradation of cellular macromolecules
A dimeric kinesin-1 molecule has 8-nm steps and can move at rates of about 1 µm/sec.
Olympic 100-meter sprinters typically run at about 180 steps per minute and can reach
speeds of about 42 km/h. With the same step size, if the Olympic runner had a step
frequency of a kinesin-1 molecule, how fast could she run? Write down your answer in
km/h, e.g. 52 km/h.
Consider a perfectly assembled clathrin cage that is composed of 12 pentagons and 20
hexagons and therefore resembles a soccer ball. How many clathrin heavy chains are
there in this cage? Write down the number as your answer, e.g. 2