Under anaerobic conditions, glycolysis provides most of the ATP that the cell needs. In
animal cells, pyruvate, the end product of glycolysis, is converted to lactic acid by
lactate dehydrogenase, as shown below:
CH3(CO)COO– + X –>CH3(CHOH)COO–+ Y
What is the correct carrier pair (in place of X and Y) in this reaction?
A.X is (ADP + Pi), and Y is (ATP)
B.X is (NADP+), and Y is (NADPH + H+)
C.X is (NAD+), and Y is (NADH + H+)
D.X is (NADH + H+), and Y is (NAD+)
E.X is (NADP++ H+), and Y is (NADPH)
During maturation of early endosomes to late endosomes, ___
A.the vacuolar domain of the endosome is shed, whereas the tubular domain is retained.
B.the endosome migrates along actin filaments away from the cell interior.
C.the lumen of the endosome becomes more acidic.
D.intralumenal vesicles disappear.
E.All of the above.
In the following schematic drawing of a vertebrate prometaphase chromosome as seen
under a microscope, indicate whether the chromosome is more likely to be closer to
pole A or pole B. Write down A or B as your answer.
Indicate true (T) and false (F) statements below regarding the regenerative capacity of
the planarian Schmidtea mediterranea. Your answer would be a four-letter string
composed of letters T and F only, e.g. TTTF.
( )When the animal is starved, some of its cells are cannibalized by other cells.
( )The differentiated cells in the animal’s body are continually replaced.
( )Even a single healthy cell can rescue a lethally irradiated animal from death.
( )Only neoblasts are capable of rescuing a lethally irradiated animal from death.
Does the nuclear-to-cytoplasmic ratio increase (I) or decrease (D) during cleavage in
early vertebrate development? Would you expect tetraploid embryos to undergo the
maternal-zygotic transition earlier (E) or later (L) compared to diploids? If the
availability of a transcription regulatory protein determines the timing of this transition,
should the protein be a transcriptional activator (A) or repressor (R)? Write down your
answer as a three-letter string using the letters in the parentheses above, e.g. IEA.
The cytoplasmic C-terminal KKXX sequence of transmembrane proteins interacts with
___
A.t-SNAREs
B.v-SNAREs
C.AP2
D.COPI coatomers
E.COPII coatomers
Which of the following types of noncoding RNA chiefly functions in the processing and
chemical modification of ribosomal RNAs (rRNAs)?
A.Small nuclear RNAs (snRNAs)
B.Small nucleolar RNAs (snoRNAs)
C.Small interfering RNAs (siRNAs)
D.Transfer RNAs (tRNAs)
E.MicroRNAs (miRNAs)
As an mRNA molecule is processed in the nucleus, it loses some proteins and binds to
new ones, some of which are used in mRNA surveillance pathways. The presence of
which of the following molecules on an mRNA is a signal that the mRNA is still NOT
ready for nuclear export?
A.Cap-binding complex
B.Exon junction complex
C.snRNPs used in splicing
D.poly-A-binding proteins
E.SR proteins
Trypanosoma cruzi uses two alternative strategies to invade its host cells. To examine
the contribution of each of these strategies to the pathogenicity, you culture mammalian
cells that can be infected with this pathogen. The cells are engineered to express green
fluorescent protein (GFP) fused to a plasma membrane protein, as well as red
fluorescent protein (RFP) fused to a lysosome-specific transmembrane protein. You
then either add only tiny latex beads (as a negative control) or add T. cruzi protozoa (to
infect the cells). After 10 minutes, you fix the cells and examine them under a
fluorescence microscope. You observe that a significant fraction (~30%) of
phagosomes/vacuoles in sample 1 are RFP-positive (i.e. show RFP fluorescence at their
membrane), whereas all phagosomes in sample 2 are RFP-negative. Which sample (1 or
2) is the one infected with T. cruzi? In this infected sample, would you expect the
RFP-negative trypanosome-containing vacuoles to be GFP-positive or GFP-negative?
A.Sample 1; GFP-positive
B.Sample 1; GFP-negative
C.Sample 2; GFP-positive
D.Sample 2; GFP-negative
In Escherichia coli, replication of DNA can occur throughout the cell cycle while the
cell is also actively transcribing its genes. This means collisions between replication
forks and RNA polymerases are inevitable. Depending on the orientation of the genes,
collisions can be rear-end (when both machines are traveling in the same direction) or
head-on (when they are traveling in opposite directions). In the following paragraph,
match each of the letters (A to D) to one appropriate number below. Do not use a
number more than once. Your answer would be a four-digit number composed of digits
1 to 5 only, e.g. 1253.
“Typically, in a rear-end collision, the (A) of RNA polymerase collides with the (B) in
the replication fork. In contrast, in a head-on collision, the (C) of RNA polymerase hits
the (D) in the fork.”
1>front edge (of RNA polymerase)
2>rear edge (of RNA polymerase)
3>DNA helicase
4>leading-strand DNA polymerase
5>lagging-strand DNA polymerase
Indicate whether each of the following descriptions better applies to an asymmetric (A)
or a symmetric (S) stem-cell division strategy. Your answer would be a four-letter string
composed of letters A and S only, e.g. AAAA.
( )It predicts the number of stem cells in a population to remain strictly constant after
several rounds of cell division.
( )Cytoplasmic factors that control stemness are localized to one side of the cell before
cytokinesis.
( )It is a more flexible strategy and can better accommodate the effect of environmental
factors.
( )It is more consistent with observations in gut stem cells and other stem cells.
What is the major way by which the monomeric G protein Ras is activated in receptor
tyrosine kinase signaling?
A.Activation of Ras-GAP
B.Activation of Ras-GEF
C.Inactivation of Ras-GAP
D.Inactivation of Ras-GEF
E.Inactivation of Ras-GDI
A genetic form of “night blindness” (i.e. poor vision in dim light) is caused by
mutations in genes encoding rhodopsin kinase (RK) and arrestin. The mutations reduce
the dynamic range of light perception, and the affected individuals have a prolonged
light response and adapt very slowly to low light (when entering a dark theater room,
for example). Which of the following mutations do you expect to be the cause?
A.Loss-of-function RK mutations and loss-of-function arrestin mutations
B.Loss-of-function RK mutations and gain-of-function arrestin mutations
C.Gain-of-function RK mutations and loss-of-function arrestin mutations
D.Gain-of-function RK mutations and gain-of-function arrestin mutations
Each single neuron acts as a computational device. Typically, the magnitude of the
combined postsynaptic potential is encoded in the … of firing of action potentials in the
postsynaptic neuron.
The following sequence logo represents the preferred cis-regulatory sequences of an
imaginary transcription regulator that functions as a dimer. Would you expect this
sequence to be recognized by a homodimer (M) or a heterodimer (T)? Write down M or
T as your answer.
Fill in the blank: Each microtubule is typically made of thirteen parallel …. that
associate laterally to form a hollow tube.
In the following pedigree, females and males are indicated by circles and squares,
respectively, and the presence of a rare disease caused by a loss-of-function mutation in
an imprinted autosomal gene is indicated by black color. Is the gene maternally
imprinted (M; i.e. not expressed from the maternally inherited chromosome) or
paternally imprinted (P)? Write down M or P as your answer.
Which reaction is normally catalyzed by the enzyme catalase in the peroxisome?
The amino acid serine has an amino group, a carboxyl group, and a hydroxyl group.
Which of the following better represents the structure of this amino acid at neutral pH?
A cross section of a developing spinal cord in a vertebrate embryo is shown in the
schematic drawing below. Indicate which feature in the drawing (labeled A to E) better
matches each of the following descriptions. Your answer would be a four-letter string
composed of letters A to E only, e.g. AAEB.
( )It contains motor neurons.
( )It is the floor plate.
( )It secretes BMP and Wnt signals.
( )It contains sensory neurons.
Indicate true (T) and false (F) statements below regarding integrin signaling. Your
answer would be a four-letter string composed of letters T and F only, e.g. TFTT.
( )Integrins usually bind their ligands with a higher affinity compared to other
cell-surface receptors.
( )Unlike cadherins, integrins usually function as individual dimers and do not cluster.
( )Anchorage dependence is mainly mediated via integrin signaling.
( )Integrins can activate the Ras-MAPK pathway.
Indicate whether each of the following descriptions better applies to forward (F) or
reverse (R) genetics. Your answer would be a four-letter string composed of letters F
and R only, e.g. RFFF.
( )It involves new gene discovery by genetic screens.
( )It may also be called genome editing.
( )In this approach, mutations are introduced deterministically in a known gene.
( )It is involved in creating knockout mice lacking a particular gene.