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Due to their high transcription rate, active ribosomal RNA (rRNA) genes can be easily
distinguished in electron micrographs of chromatin spreads. They have a characteristic
"Christmas tree" appearance, where the DNA template is the "trunk" of the tree and the
nascent RNA transcripts form closely packed "branches." At the base of each branch is
an RNA polymerase extending that branch, while RNA processing complexes at the tip
of the branch form terminal "ornaments." The top of the tree represents the ___ of the
rRNA gene, and the "ornaments" are at the ___ end of the nascent rRNA molecules.
A.end; 3'
B.end; 5'
C.beginning; either 3' or 5'
D.beginning; 3'
E.beginning; 5'
In which of the following groups of viruses is an RNA-dependent RNA polymerase
packaged as a structural protein in each newly made viral particle?
A.DNA viruses
B.Viruses with a positive [+] strand RNA genome
C.Viruses with a negative [-] strand RNA genome
D.Retroviruses
E.Viruses with a part single- and part double-stranded DNA genome
Consider a transcription regulatory protein (A) that can bind to a promoter (p). After
reaching an initial steady state, the concentration of A is suddenly increased tenfold.
The following graph shows the formation of A:p over time after this change for two
systems, one of which is described by higher koff and kon values compared to the other.
Which curve (1 or 2) corresponds to this system? Write down 1 or 2 as your answer.
In contrast to transporters, the channel proteins in cellular membranes ___
A.interact strongly with the solute(s) that they transport.
B.undergo a conformational change every time they transport a solute.
C.can only mediate passive transport.
D.form pores that are always open.
Which of the following is correct regarding the composition of various biological
membranes?
A.Bacterial plasma membranes are often composed of one main type of phospholipid
and lack cholesterol.
B.Cholesterol in the eukaryotic plasma membrane induces phase transition to the gel
state.
C.Inositol phospholipids are the most abundant lipids in the endoplasmic reticulum
membrane.
D.The mitochondrial and bacterial membranes are rich in glycolipids.
E.Yeast cells synthesize more fatty acids with cis-double bonds when the temperature in
the environment rises.
In the following schematic drawing of a Holliday junction that undergoes branch
migration, cutting at which combination of the sites a to d would generate a crossover?
A.a and b
B.a and c
C.a and d
D.b and c
E.b and d
The transmembrane protein Tango1 is a packaging protein that helps some secretory
proteins leave the endoplasmic reticulum (ER) after synthesis. Knocking down Tango1
by RNA interference impairs the incorporation of collagen VII, but not collagen I, into
transport vesicles destined for the Golgi apparatus. The protein contains a lumenal
N-terminal SH3 domain and a cytosolic C-terminal proline-rich domain. Which of the
following proteins would you expect to interact with the N-terminal and C-terminal
domains of Tango1, respectively?
A.Procollagen VII; COPI components
B.Procollagen VII; COPII components
C.Procollagen I; COPI components
D.Procollagen I; COPII components
E.COPI components; procollagen I
You have prepared glass beads coated with rabbit anti-Ig antibodies that were isolated
from rabbits that were immunized with mouse immunoglobulin (Ig). If you incubate a
sample of mononucleated cells from mouse spleen with these beads, which of the
following cell types do you think would stick to the beads?
A.Only macrophages
B.Only B cells
C.Only cytotoxic T cells
D.B cells and cytotoxic T cells
E.B cells and macrophages
Regulation of the Ci (Cubitus interruptus) protein in the Hedgehog signaling pathway is
reminiscent of that of -catenin in the Wnt pathway. Which of the following features is
shared among these two proteins?
A.Both proteins are ubiquitylated when the signal (Hedgehog or Wnt) is present.
B.Both proteins are able to enter the nucleus only in the absence of the signal.
C.Both proteins can be phosphorylated by GSK3 and CK1 in the absence of the signal.
D.Both proteins are fully degraded by the proteasome in the absence of the signal.
E.None of the above.
Which of the following statements is true regarding skeletal muscle development and
regeneration in humans?
A.Muscle is among those tissues that cannot be renewed once damaged.
B.Myoblasts are multipotent stem cells.
C.Muscle regeneration occurs as a result of stimulation of quiescent stem cells in the
periphery of muscle fibers.
D.A muscle that has been repaired once cannot be repaired again.
The focal adhesion kinase ...
A.is a cytosolic serine/threonine kinase.
B.binds directly to integrin dimers.
C.can be phosphorylated by Src kinases.
D.prevents the relay of outside-in integrin signaling.
E.All of the above.
Which of the following spontaneous lesions in DNA occurs most frequently in a
mammalian cell?
A.Depurination
B.Cytosine deamination
C.Guanine oxidation
D.Guanine alkylation
E.Depyrimidination
Indicate true (T) and false (F) statements below regarding the nuclear transport of
proteins. Your answer would be a four-letter string composed of letters T and F only,
e.g. TTTF.
( )Many nuclear import and export receptors are members of the same protein family.
( )Most nuclear import receptors contain unstructured domains with FG-repeats.
( )Adaptor proteins that simultaneously bind to nuclear localization signals and to
importins are required for the import of some nuclear cargo proteins.
( )Ran is mostly found in its GTP-bound form in the nucleus.
Indicate true (T) and false (F) statements below regarding a genome and its evolution.
Your answer would be a four-letter string composed of letters T and F only, e.g. FFTF.
( )The genome of the last common ancestor of mammals can be investigated only if a
DNA sample of the ancestor can be obtained.
( )All of the "ultraconserved" elements found in the human genome have been shown to
encode long noncoding RNAs.
( )If a mouse carrying a homozygous deletion of a highly conserved genomic sequence
survives and shows no noticeable defect, the highly conserved sequence has to be
functionally unimportant.
( ) The "human accelerated regions" are genomic regions that are found in humans with
no homologs in chimpanzees or other animals.
Fill in the blank in the following paragraph regarding the innate and adaptive immune
systems. Do not use abbreviations.
"As key components of the innate immune response, ... cells provide the link between
the innate and adaptive immune responses. Upon exposure to pathogens in tissues, they
engulf the microbe, become activated, and travel to nearby lymphoid organs where they
present the processed antigens to the lymphocytes of the adaptive immune system."
Indicate whether each of the following descriptions better applies to COPI- (1), COPII-
(2), or clathrin- (3) coated vesicles. Your answer would be a four-digit number
composed of digits 1 to 3 only, e.g. 1322.
( )They are uncoated by an hsp70 family protein, which is stimulated by the binding of
auxilin.
( )They keep their coat proteins for a relatively long time, until they dock onto their
target membrane.
( )Their uncoating depends on activation of an ARF-GAP.
( )Their uncoating depends in part on activation of a Sar1-GAP.
Neurotransmitters are retrieved from the synaptic cleft soon after their release from the
presynaptic axon terminal. Do you think treatment of neurons with the drug dynasore, a
dynamin inhibitor, would affect this retrieval positively (P) or negatively (N)? Write
down P or N as your answer.
In the following schematic diagram, the estimated attractive or repulsive force between
two adhesive cells is plotted as a function of distance between the cells. The dashed
curve represents a condition under which the cells express cadherin but not N-CAM.
The other two curves represent conditions under which both cadherin and heavily
sialylated N-CAM are expressed. In one of the conditions, however, the ionic strength
of the medium has been artificially increased by addition of salt. Which curve (1 or 2)
do you think represents the high-salt condition? Write down 1 or 2 as your answer.
