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Using Cre recombination, the gene encoding stem cell factor (SCF) can be deleted in
specific cell types in adult mice. Deletion of this gene in which of the following cells
would you expect to lead to the most significant depletion of hematopoietic stem cells
in the bone marrow?
A.Osteoblasts
B.Osteoclasts
C.Stromal cells
D.Hematopoietic stem cells
E.Common myeloid precursor cells
A protein that is normally not expressed in epithelial cells has been induced in these
cells and has been engineered such that a GPI anchor is attached to it as it is processed
in the ER. Would you expect to find this protein in the apical (A) or basolateral (B)
domain of the plasma membrane in these cells? Write down A or B as your answer.
The signal-recognition particle (SRP) ___
A.is a heterodimeric protein.
B.transiently inhibits translation and polypeptide elongation by binding to and
inhibiting the elongation factors.
C.accompanies the nascent polypeptide all the way into the ER lumen.
D.binds GTP.
E.is permanently attached to the cytosolic face of the ER membrane, thus bringing the
ribosomes into close proximity of the translocon.
Genetically knocking out both copies of the p53 gene in rats ...
A.is embryonic lethal.
B.results in a lower malignancy rate, but the rats are otherwise seemingly normal.
C.results in a higher rate of cancer onset, but the rats are otherwise seemingly normal.
D.increases cell death by apoptosis, leading to developmental defects.
E.does not have any effect unless the rats live outside of the laboratory and are exposed
to various types of stress.
Bacteria contain homologs of cytoskeletal filament subunits ...
A.except those of the intermediate filaments.
B.but these homologs are incapable of nucleotide binding and hydrolysis.
C.that are less diverse in their function relative to their eukaryotic counterparts.
D.that can have different functions to those of their eukaryotic counterparts.
E.that are dispensable for cell growth and proliferation.
Mammalian Cdk inhibitor proteins (CKIs) can be grouped into two families based on
their structural and functional differences. The Cip/Kip family proteins (e.g. p21) have a
broad binding specificity. These proteins bind preferentially to already formed
cyclin-Cdk complexes and thus enhance complex formation. However, they inhibit the
kinase activity of most complexes (e.g. S-Cdks), except in the case of G1-Cdk
complexes where no inhibition occurs. Consequently, Cip/Kip family proteins have an
overall positive effect on Cdk4/6 activity due to their help in bringing the subunits
together. In contrast, the inhibitors of the INK4 family (e.g. p16) bind only to the Cdk
subunit of G1-Cdks and prevent binding of both the G1 cyclins and the Cip/Kip family
CKIs. Based solely on these findings, would you expect p16 to activate (A) or
inactivate (I) the S-Cdks in the presence of limited amounts of p21?
Sort the following events to reflect the order in which they occur in the presentation of
viral peptides to cytotoxic T cells by a virus-infected cell. Your answer would be a
four-letter string composed of letters A to D only, e.g. BDCA.
(A)Peptide transport into the ER lumen
(B)Partial proteasomal degradation of the viral protein into peptide fragments
(C)Peptide binding to class I MHC protein in the ER lumen
(D)The appearance of viral protein in the cytosol
Which of the following classes of noncoding RNAs is NOT directly involved in RNA
interference?
A.miRNA
B.snoRNA
C.piRNA
D.siRNA
All blood cells in our body ...
A.have exceptionally short life-spans-at most a month or so.
B.are produced only before adulthood.
C.are ultimately generated from multipotent hematopoietic stem cells.
D.are made from progenitors that themselves circulate in the blood.
E.All of the above.
A certain neuron in a mouse brain is firing about 300 times per second, whereas almost
all of its neighboring neurons are firing at much lower rates of only a few times per
second. This implies that ...
A.this neuron expresses more depolarizing (Na+ and Ca2+) than hyperpolarizing (K+)
channels compared to most of its neighbors.
B.the mouse is experiencing an epileptic seizure.
C.the refractory period of its voltage-gated Na+ channels is at least 300 ms.
D.it releases excitatory neurotransmitters at its axon terminals.
E.it is probably of a different type compared to most of its neighbors.
Which of the following is NOT correct regarding homologous recombination and its
regulation?
A.Loss of heterozygosity can occur if a broken chromosome is repaired using a sister
chromatid instead of its homologous chromosome.
B.Repair of double-strand breaks by homologous recombination is favored during or
soon after DNA replication.
C.Homologous recombination can rescue broken or stalled replication forks in S phase.
D.Excessive use of homologous recombination by human cells can lead to cancer.
E.Low usage of homologous recombination by human cells can lead to cancer.
Fill in the blank in the following paragraph. Do not use abbreviations.
"Particularly abundant in cells of heart muscle and the epidermis, ... are structurally
similar to adherens junctions and contain a number of homologous components.
However, their cadherin molecules are linked to intermediate filaments instead of the
actin cytoskeleton."
In the following diagram showing the overall flow of genetic information in all living
cells, what is the name of the process indicated with a question mark?
Indicate true (T) and false (F) statements below regarding DNA methylation in humans.
Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF.
( )Methylation of adenines is the most common DNA methylation in humans.
( )Methylated cytosine can be accidentally deaminated to produce thymine, leading to a
C-to-T transition.
( )Cytosine methylation often occurs within a 5'-CG-3' sequence.
( )Shortly after fertilization, a genome-wide wave of demethylation takes place.
For each of the following classifications, indicate whether you would expect to find an
actively transcribed gene in the first category (1) or the second (2). Your answer would
be a six-digit number composed of digits 1 and 2 only, e.g. 222121.
( )1: Heterochromatin, or 2: euchromatin
( )1: Chromosome puffs, or 2: condensed chromosome bands
( )1: Nuclear periphery, or 2: the center of the nucleus
( )1: Within the chromosome territory, or 2: extended out of the territory
( )1: Apart from, or 2: close to actively transcribed genes within the nucleus
( )1: 11-nm "beads-on-a-string" fibers, or 2: 30-nm fibers
Consider Agrin signaling in the formation of neuromuscular junctions in vertebrates.
Shp2 is a protein tyrosine phosphatase that counteracts the tyrosine kinase activity of
MuSK. Rapsyn interacts with the acetylcholine receptors and induces their
agrin-dependent clustering. Indicate whether each of the following is expected to
enhance (E) or suppress (S) acetylcholine receptor clustering in this process. Your
answer would be a four-letter string composed of letters E and S only, e.g. EEEE.
( )Specific inhibition of Shp2
( )Loss of Rapsyn
( )Loss of LRP4
( )Constitutive activation of MuSK
