Indicate which of the following enzymatic activities corresponds to A, B, or C in the
following schematic drawing of DNA methylation events in the human genome. Your
answer would be a three-letter string composed of letters A, B, and C only, e.g. CBA.
( )DNA demethylating enzyme
( )Maintenance methyl transferase enzyme
( )De novo methyl transferase enzyme
The majority of transcription regulators make sequence-specific contacts with DNA in
the major groove. In the two diagrams below, where are the contact surfaces that are
exposed in the major groove?
A.1, 3
B.1, 4
C.2, 3
D.2, 4
Consider two cells attached to each other via adherens junctions. The forces generated
by the actin cytoskeleton in one cell …
A.are dependent on myosin activity.
B.are normally balanced by similar forces in the neighboring cell.
C.can strengthen the adherens junction by unfolding catenin proteins.
D.All of the above.
Sort the following molecules from a low to high rate of diffusion inside the cytosol.
Your answer would be a four-letter string composed of letters A to D only, e.g. ADCB.
(A)Myoglobin (a protein)
(B)Glycine (an amino acid)
(C)Ribosome (a protein-RNA complex)
(D)CO2
If cells that have started mitosis are treated with nocodazole, a drug that depolymerizes
microtubules, what would you expect to happen? Where would you expect Mad2
protein to be localized?
A.The cells would arrest in prometaphase; Mad2 would be localized to the spindle
poles.
B.The cells would arrest in telophase; Mad2 would be localized to the spindle poles.
C.The cells would immediately enter anaphase, finish mitosis, and enter G1; Mad2
would be localized to the spindle poles.
D.The cells would arrest in prometaphase; Mad2 would be localized to almost all
kinetochores.
E.The cells would arrest in telophase; Mad2 would be localized to almost all
kinetochores.
Which of the following motor proteins are more directly involved in anaphase B?
A.Kinesin-5 on interpolar microtubules and dynein on kinetochore microtubules
B.Kinesin-13 on kinetochore microtubules and dynein on astral microtubules
C.Kinesins 4 and 10 on interpolar and astral microtubules and dynein on kinetochore
microtubules
D.Kinesin-5 on interpolar microtubules and kinesins 4 and 10 on interpolar and astral
microtubules
E.Kinesin-5 on interpolar microtubules and dynein on astral microtubules
Mutation in which of the following genes is most prevalent in human colorectal cancer
cells?
A.K-Ras
B. -Catenin
C.Apc
D.p53
E.MLH
At physiological pH, what is the approximate net charge of a hexapeptide with the
following amino acid sequence?
Asp-Val-Ile-Glu-Arg-Ser
A.-2
B.-1
C.0
D.+1
E.+2
The observation that proteins often renature into their original conformations after they
have been unfolded by denaturing solvents implies that €¦___
A.the information needed to specify the three-dimensional shape of a protein is encoded
in its amino acid sequence.
B.the cell does not need molecular chaperones for survival.
C.the final folded structure of a protein is usually NOT the one with the lowest free
energy.
D.each protein folds into several different conformations inside the cell.
E.All of the above.
Only cells that express a puromycin-resistance (PR) gene can grow in the presence of
the drug puromycin. Ganciclovir is a nontoxic drug that is converted to a lethal toxin in
a cell that expresses thymidine kinase (TK). Thy-1 is a fibroblast-specific marker
protein. Which of the following selection strategies is the most reasonable one to use in
experiments that attempt to generate induced pluripotent stem cells (iPS cells) from
fibroblasts?
A.Engineering fibroblasts to express PR under the control of the Nanog promoter, and
selecting iPS cells in puromycin-containing media
B.Engineering fibroblasts to express PR under the control of the Thy-1 promoter, and
selecting iPS cells in puromycin-containing media
C.Engineering fibroblasts to express TK under the control of the Nanog promoter, and
selecting iPS cells in ganciclovir-containing media
D.Engineering fibroblasts to express TK under the control of the Thy-1 promoter, and
selecting iPS cells in ganciclovir-containing media
E.Engineering fibroblasts to express TK under the control of the Thy-1 promoter, and
selecting iPS cells in puromycin-containing media
By forming over 100 pinocytic vesicles per minute, a macrophage ingests over 10% of
its own volume of fluid every half an hour. This is equivalent to ingesting about 100%
of the macrophage’s plasma membrane. If the average volume of a macrophage is about
450 3 and its average surface area is about 750 2, what is the average diameter
of the early pinocytic vesicles in the cell? Assume spherical vesicles. The formulas for
the volume (V) and surface area (S) of a sphere of radius r are V = 4/3 x x r3, and S =
4 x x r2, respectively. Write down your answer in nanometers, with no decimals, e.g.
830 nm.
Consider a signaling protein that can be phosphorylated by a dual-specificity protein
kinase at two independent sites (one tyrosine and one serine residue), such that each site
is phosphorylated in about 1% of the protein molecules under normal conditions.
Phosphorylation at the first site has a short half-life, since a fast tyrosine phosphatase
removes the phosphate soon after the residue is phosphorylated, whereas
dephosphorylation at the second site-carried out by a serine/threonine phosphatase-is
relatively slow. Upon activation of a signaling pathway, the concentration of the
dual-specificity kinase increases several-fold rapidly. The phosphorylation state of the
tyrosine and serine residues following stimulation is compared in the following graph.
Which curve (1 or 2) do you think corresponds to the serine residue? Write down 1 or 2
as your answer.
Indicate if each of the following descriptions matches lithotrophic (L), organotrophic
(O), or phototrophic (P) organisms. Your answer would be a four-letter string composed
of letters L, O, and P only, e.g. LLPP.
( ) They feed on other living organisms or their organic products.
( ) They are responsible for the current oxygen-rich atmosphere of the Earth.
( ) They are all known to be prokaryotic.
( ) They are the primary energy converters in hydrothermal vents in the ocean floor.
Indicate true (T) and false (F) statements below regarding apoptosis in disease. Your
answer would be a four-letter string composed of letters T and F only, e.g. TTTF.
( )Either excessive or insufficient apoptosis can contribute to disease.
( )Excessive apoptosis, in many cases, leads to autoimmune disease and cancer.
( )In about half of human cancers, the tumor suppressor protein p53 is mutated.
( )Drugs that interfere with the function of Bcl2 family proteins such as Bax and Bak
may treat cancers by stimulating apoptosis.
From an evolutionary perspective, which mating pattern confers a higher fitness to a
mammalian population: preferred mating between pairs whose MHC genes are most
similar (S) or between those whose MHC genes are most dissimilar (D)? Write down D
or S as your answer.
Indicate true (T) and false (F) statements below regarding the ubiquitin ligase c-Cbl.
Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF.
( )It contains an SH2 domain, and can therefore activate RTK signaling.
( )It ubiquitylates activated RTKs.
( )Its overactivation can lead to prolonged RTK signaling and promote the development
of cancer.
( )It is part of a negative feedback loop to down-regulate RTKs.
In cells that are exposed to sunlight, ultraviolet (UV) light can result in covalent linkage
between two adjacent DNA bases. If not repaired in time, such dimers can lead to
inheritable mutations. Consider the sequence 5′-GGTATGATCATTATAA-3′ in the
chromosome of a cell that is exposed to intense sunlight. How many possible dimers
can form in the region of DNA double helix corresponding to this sequence?
In the schematic graphs below, the red color indicates high gene expression and blue
color indicates low gene expression. The expression level is plotted as a function of the
concentrations of two transcription regulatory proteins, A1 and A2. Which graph (1 or
2) do you think corresponds to an “AND NOT” combinatorial logic? Write down 1 or 2
as your answer.
Indicate true (T) and false (F) statements below regarding the cellular metabolism of
nucleotides and amino acids. Your answer would be a four-letter string composed of
letters T and F only, e.g. TTTT.
( )Nitrogen fixation occurs in the mitochondria in most animal cells to generate amino
acids.
( )All 20 natural amino acids must be provided in our diet and are therefore “essential.”
( )There are NO essential nucleotides that must be provided in the diet.
( )Catabolism of amino acids in our body leads to the production of urea which is
excreted.