What determines the time and place that a certain gene is transcribed in the cell?
A.The type of cis-regulatory sequences associated with it
B.The relative position of cis-regulatory sequences associated with it
C.The arrangement of various cis-regulatory sequences associated with it
D.The specific combination of transcription regulators present in the nucleus
E.All of the above
How fast does a bacterial ribosome move on an mRNA?
A.At about 2 nucleotides per second, significantly lower than the speed of the RNA
polymerase.
B.At about 5 nucleotides per second, comparable to the speed of the RNA polymerase.
C.At about 10 nucleotides per second, significantly lower than the speed of the RNA
polymerase.
D.At about 20 nucleotides per second, comparable to the speed of the RNA polymerase.
E.At about 60 nucleotides per second, comparable to the speed of the RNA polymerase.
DNA and RNA polymerase differ in all of the following EXCEPT___
A.the nucleotide substrates they incorporate.
B.their requirement for a primer.
C.their error rate.
D.the type of chemical reaction they catalyze.
E.their processivity.
On the plasma membrane of the archaeon Halobacterium salinarum, bacteriorhodopsin
is found in high density in patches of purple membrane. This protein ___
A.is a light-gated anion channel.
B.is a single-pass transmembrane protein.
C.uses the energy stored in the proton gradient to transport small molecules.
D.changes conformation in response to light.
E.All of the above.
Which of the following phosphoinositides is the preferred binding target for a
PH-domain-containing protein?
What group of mobile genetic elements is largely responsible for the resistance of the
modern strains of pathogenic bacteria to common antibiotics?
A.DNA-only transposons
B.Retroviral-like retrotransposons
C.Nonretroviral retrotransposons
D.Site-specific recombinases
Which one of the following chromosomes has formed stable attachment(s) to the
spindle microtubules?
Under certain conditions, about 20 molecules, on average, are predicted to exist in each
-octylglucoside detergent micelle. If the critical micelle concentration for this
detergent is about 20 mM under these conditions, at what total -octylglucoside
concentration are about half of the detergent molecules found in micelles?
A.1 mM
B.10 mM
C.20 mM
D.21 mM
E.40 mM
After gaining entry into the host cell by the zipper mechanism, the bacterium Listeria
monocytogenes escapes phagosomes by secreting listeriolysin O. This protein …
A.is active at neutral pH and cannot be degraded by the proteasome.
B.is active at neutral pH and is rapidly degraded by the proteasome.
C.is active at acidic pH and cannot be degraded by the proteasome.
D.is active at acidic pH and is rapidly degraded by the proteasome.
B.is active at basic pH and cannot be degraded by the proteasome.
Indicate whether each of the following descriptions better applies to these poles
established in an early embryo: anterior (A), posterior (P), dorsal (D), ventral (V),
animal (N), or vegetal (G). Your answer would be a six-letter string composed of letters
A, D, G, N, P, and V only, e.g. ADGPVN.
( )It defines the part to become internalized in gastrulation.
( )It defines the parts to remain external.
( )It defines the location of the future head.
( )It defines the location of the future tail.
( )It defines the location of the future belly.
( ) It defines the location of the future back.
Expression of the Even-skipped (Eve) gene in early Drosophila embryos is under the
control of several transcription regulators. In one example, one of the Eve stripes is
positioned near the anterior region of the embryo, and its regulatory module contains
binding sites for Bicoid and Hunchback (activators) as well as Giant and Kr¼ppel
(inhibitors) such that the gene is expressed only in the region where concentrations of
the two activators are high and the concentrations of the two inhibitors are low. A
reporter gene can be placed under the control of this module, and it can be shown to
form a stripe in the same place in the embryo as the corresponding stripe of Eve.
Answer the following question(s) based on these findings.
In the Eve regulatory modules, the binding sites for Giant and Kr¼ppel are usually
close to, or even overlapping with, those of Bicoid and Hunchback. This implies that
Eve expression is regulated by ___ between the activators and regulators.
A.Feedback regulation
B.Cooperation
C.Competition
D.Feed-forward regulation
Indicate whether each of the following normally occurs before (B) or after (A) antigen
stimulation of B cells. Your answer would be a four-letter string composed of letters A
and B only, e.g. AAAA.
( )V(D)J recombination
( )Class switch recombination
( )Somatic hypermutation
( )Junctional diversification
Which of the following morphological changes is NOT typically seen in a cell that is
undergoing apoptosis?
A.The cell rounds up.
B.The nuclear envelope disassembles.
C.The cell swells.
D.Large cells break up into membrane-enclosed fragments.
E.The nuclear chromatin breaks into fragments.
Indicate whether each of the following examples better applies to commensalism (C),
mutualism (M), or parasitism (P) in the interaction between a host and a microbe. Your
answer would be a four-letter string composed of letters C, M, and P only, e.g. CCPP.
( )Due to poor public sanitation, a child catches cholera.
( )A mouse is infected with a virus but shows no noticeable health defect whatsoever.
( )Biotin and other vitamins produced by intestinal microbiota are regularly absorbed in
the human intestine.
( )Bacteria on the skin of cattle produce antifungal compounds.
Which of the following is true regarding retroviral-like retrotransposons?
A.They encode both a reverse transcriptase and an RNA polymerase.
B.They have directly repeated long terminal repeats at their two ends when integrated
into chromosomal DNA.
C.Their genomic RNA can be translated to produce viral coat proteins.
D.They leave double-strand breaks in the original donor DNA.
E.The Alu element in our genome is an example of retroviral-like retrotransposons.
Indicate true (T) and false (F) statements below regarding electron microscopy. Your
answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( )Depending on acceleration voltage, the resolution limit of an electron microscope can
be as small as 0.05 nm.
( )The emission gun and the magnetic coils in an electron microscope are analogous to
the light source and the glass lenses in a light microscope, respectively.
( )Contrast in specimens for electron microscopy can be achieved using electron-dense
material.
( )For biological samples, the effective resolution of electron microscopy is about 1 nm.
The schematic drawing below summarizes the differentiation of ntive helper T cells
(TH cells) into various effector T cells, which occurs in a peripheral lymphoid organ.
Indicate which effector cell (A to E) in the drawing is better described by each of the
following descriptions. Your answer would be a four-letter string composed of letters A
to E only, e.g. DEAE.
( )It can also develop from thymocytes in the thymus, as well as from TH cells.
( )It suppresses the development, activation, or function of most other immune cells.
( )It produces IFN and activates macrophages.
( )They reside in lymphoid follicles close to developing B cells.
In the following graphs, the cellular response, as measured in real time by the
concentration of a certain active effector protein, is plotted over time for five cell types
(A to E) that are treated with three different concentrations of a signal molecule. During
the time period indicated by the horizontal gray bar, the signal molecule is present in
the culture media at a concentration of 1 nM (dotted curve), 5 nM (gray curve), or 25
nM (solid curve). Answer the following question(s) based on these graphs.
Which of the cell types A to E shows the widest dynamic range of signal concentration?
Migration of proteins during separation by SDS polyacrylamide-gel electrophoresis
(SDS-PAGE) is generally related to the logarithm of their molecular weight, as depicted
in the qualitative graph below. If a protein mixture containing proteins of evenly
distributed molecular weights (e.g. 10, 20, 30, 40, etc.) is separated by SDS-PAGE,
which of the following staining patterns would you expect to observe?
Indicate whether each of the following cell-surface proteins is expressed mainly by B
cells (B), dendritic cells (D), or T cells (T). Your answer would be a four-letter string
composed of letters B, D, and T only, e.g. DBBB.
( )Co-stimulatory protein B7, which is recognized by CD28
( )Invariant CD3 complex
( )Inhibitory CTLA4 protein
( )CD40 receptor, which recognizes the co-stimulatory protein CD40 ligand on a helper
T cell