The duty ratio for a motor protein is defined as the fraction of time in each cycle of
activity of the motor in which the head is bound with high affinity to its cytoskeletal
track. Which of the following is reasonable given this definition?
A.Myosin V has a higher duty ratio than myosin II, because Pi release is the
rate-limiting step in its cycle.
B.Myosin II has a higher duty ratio than myosin V, because Pi release is the
rate-limiting step in its cycle.
C.Myosin V has a higher duty ratio than myosin II, because ADP release is the
rate-limiting step in its cycle.
D.Myosin II has a higher duty ratio than myosin V, because ADP release is the
rate-limiting step in its cycle.
During DNA replication in the cell, DNA primase makes short primers that are then
extended by the replicative DNA polymerases. These primers ___
A.are made up of DNA.
B.generally have a higher number of mutations compared to their neighboring DNA.
C.are made more frequently in the leading strand than the lagging strand.
D.are joined to the neighboring DNA by DNA ligase.
E.provide a 3′-phosphate group for the DNA polymerases to extend.
A DNA-binding protein recognizes a specific eight-nucelotide sequence in DNA.
Assuming that its binding is perfectly specific, how many binding sites are expected to
exist for it in human genomic DNA, which is composed of about 6 x 109 nucleotide
pairs? What about if the protein forms a homodimer? Note that the target sequence can
be oriented either way in the double-stranded DNA.
A.About 200,000; about 30,000
B.About 2000; about 300
C.About 200; about 30
D.About 200,000; about 300
E.About 200,000; about 3
Which of the following correlates the best with biological complexity in eukaryotes?
A.Number of genes per chromosome
B.Number of chromosomes
C.Number of genes
D.Genome size (number of nucleotide pairs)
Scientists discover more than ten thousand new species of living organisms every year.
What is shared between all of these organisms?
A.They are made of cells, whose nuclei enclose their DNA.
B.They obtain their energy from sunlight.
C.They produce and use adenosine triphosphate (ATP).
D.Their genome contains at least 1000 genes.
E.All of the above.
Most GTPases are present inside the cell at a much higher concentration than their
upstream GAP and GEF proteins. Imagine a mutation in a certain GTPase, such as a
Rab protein, resulting in an extremely tight binding between the GTPase and its GEF,
and a very slow dissociation. What would you expect to happen in the cell as a result?
A.Rab proteins will be activated, because the tightly bound GEFs will be unavailable.
B.Rab proteins will be inactivated, because the tightly bound GEFs will be unavailable.
C.Rab proteins will be activated, because the Rab-GAPs will become activated.
D.Rab proteins will be inactivated, because their GAPs will become activated.
E.Rab proteins will be activated, because there are fewer GAPs available.
How does the affinity of M6P receptor proteins for the mannose 6-phosphate marker
change between the TGN and early endosome? Which coat protein is mainly
responsible for their transport from the TGN to the endosome?
A.The affinity is higher in the TGN; clathrin
B.The affinity is higher in the TGN; retromer
C.The affinity is higher in endosomes; clathrin
D.The affinity is higher in endosomes; retromer
Imagine a segment of DNA (within a gene) encoding a certain amount of information in
its nucleotide sequence. When this segment is fully transcribed into mRNA and then
translated into protein, in general, ___
A.the protein sequence would carry more information compared to the DNA and
mRNA sequences, because its alphabet has 20 letters.
B.the protein sequence would carry less information compared to the DNA and mRNA
sequences, because several codons can correspond to one amino acid.
C.the amount of information in the mRNA sequence is lower, because the mRNA has
been transcribed using only one of the DNA strands as the template.
D.the amount of information in the mRNA sequence is higher, because several mRNA
molecules can be transcribed from one DNA molecule.
The microtubule-binding protein Patronin binds to the minus ends of microtubules at
the spindle pole and protects them from the effect of catastrophe factors. If Patronin
activity is inhibited by injecting an anti-Patronin antibody into Drosophila melanogaster
embryos prior to cellularization, anaphase B is suppressed and the spindles are
significantly shorter. Which of the forces (1 or 2) in the following schematic diagram do
you think is mostly responsible for anaphase B in this organism at this stage? Does the
effect of Patronin inhibition resemble that of kinesin-5 inhibition (I) or overactivation
(O)?
A.1; I
B.1; O
C.2; I
D.2; O
You have karyotyped cells from two colorectal tumor samples, one from a hereditary
nonpolyposis colorectal cancer (HNPCC) patient, and the other from a familial
adenomatous polyposis coli (FAP) patient. One group of the karyotypes shows gross
chromosomal abnormalities with extra or deleted chromosomes and several
translocations and deletions. The other group, however, is almost normal, and
comparable to noncancerous samples. Which group would you expect to have
loss-of-function mutations in the DNA mismatch repair system genes MSH2 and MLH1
as their primary driver mutations?
A.HNPCC, which has an almost normal karyotype
B.HNPCC, which has a grossly abnormal karyotype
C.FAP, which has an almost normal karyotype
D.FAP, which has a grossly abnormal karyotype
What is the effect of defective or missing N-acetylglucosamine phosphotransferase on
lysosomal protein sorting?
A.Lysosomal proteins are secreted from the cell.
B.Lysosomal proteins are retained in the Golgi network.
C.Lysosomal proteins are retained in the ER.
D.Lysosomal proteins remain tightly bound to M6P receptors.
E.Nonfunctional lysosomal proteins accumulate in the lysosome.
Indicate true (T) and false (F) statements below regarding glycosaminoglycan chains in
the extracellular matrix. Your answer would be a four-letter string composed of letters T
and F only, e.g. TFTT.
( )They are highly branched polysaccharides.
( )They are strongly hydrophilic and absorb a large amount of water.
( )They all contain N-acetylglucosamine or N-acetylgalactosamine.
( )They are highly positively charged.
For each of the following proteins that are proteolytically cleaved in apoptosis, indicate
whether the cleavage is first carried out by an initiator (I) or executioner (E) caspase.
Your answer would be a five-letter string composed of letters I and E only, e.g. EEEII.
( )The initiator caspase-2
( )The executioner caspase-3
( )The BH3-only protein Bid
( )The endonuclease inhibitor iCAD
( )The nuclear protein Lamin A
Your friend who is studying the sequence conservation around the branch-point site on
a subset of pre-mRNAs in Macaca mulatto (rhesus macaque) has sent you the following
sequence logo of the region of interest, but has forgotten to indicate the position of the
branch-point nucleotide itself within this region. Where do you think it is? Write down
the position number (1 to 8) as your answer.
Indicate whether the epithelium in each of the following organs is (Y) or is not (N) kept
almost sterile in a healthy human. Your answer would be a four-letter string composed
of letters Y and N only, e.g. YYYY.
( )Bladder
( )Cervix
( )Lower lung
( )Colon
Indicate true (T) and false (F) statements below regarding cellular control of growth and
division. Your answer would be a four-letter string composed of letters T and F only,
e.g. TFTF.
( )Replicative cell senescence usually arises due to the accumulation of mutations in
genes encoding S- and M-cyclins.
( )Replicative cell senescence is caused by the induction of apoptosis by p53.
( )Excessive mitogenic stimulation can result in Mdm2 activation and the induction of
apoptosis or cell-cycle arrest.
( )The Mdm2 inhibitor Arf induces cell-cycle progression.
Indicate whether each of the following descriptions better applies to receptor-mediated
endocytosis (R), phagocytosis (F), pinocytosis (P), or macropinocytosis (M). Your
answer would be a four-letter string composed of letters R, F, P, and M only, e.g.
MMPF.
( )This pathway depends on caveolin and cavin proteins.
( )Pathogenic particles such as SV40, papillomavirus, and cholera toxin enter the cell
via this pathway.
( )In animals, this pathway is normally limited to professional cells such as neutrophils.
( )This pathway proceeds by the formation of highly ruffled regions in the plasma
membrane which then collapse, resulting in fluid uptake.
In mammals, colostrum (or “first milk”) is produced by the mother in late pregnancy
and shortly after giving birth to feed the newborn. In addition to nutrients, it is
particularly rich in antibodies that are absorbed through the intestinal epithelium and
support the weak immune system of the infant. Occasionally, some infants suffer from
either respiratory acidosis or alkalosis. In acidosis, the blood pH becomes acidic due to
lack of sufficient ventilation, while the opposite happens in alkalosis due to
hyperventilation. Considering the molecular mechanism of transcytosis in intestinal
epithelia, which of these conditions-acidosis (C) or alkalosis (L)-would you expect to
interfere more with antibody absorption by transcytosis in these infants? Write down C
or L as your answer.