Lampbrush chromosomes ___
A.are transcriptionally inactive.
B.are readily observed in the oocytes of humans and insects.
C.have thousands of duplicated DNA molecules arranged side by side.
D.are mitotic chromosomes with two sister chromatids attached together only at the
centromere.
E.are thought to have a structure that is relevant to mammalian chromosomes in
interphase.
Once the molecular aberrations in a cancer are understood, drugs can be designed with
a rational approach to treat the cancer. Which of the following is NOT true regarding
such drugs?
A.The drug imatinib (Gleevec ) can inhibit the chimeric tyrosine kinase Bcr-Abl in
chronic myelogenous leukemia (CML).
B.Even if a protein is not the product of a cancer-critical gene, drugs that specifically
block its activity can be effective in curing cancer.
C.Imatinib is most effective in treating chronic myelogenous leukemia (CML) in its
acute blast-crisis phase.
D.Protein kinases have turned out to be relatively easy to inhibit with small molecules.
E.The success of imatinib relies on the phenomenon of oncogene dependence in cancer
cells.
Despite their overall similarity, NADH and NADPH are not used indiscriminately by
the cell. What are the distinctive features of these two carrier molecules?
A.NADPH has an extra phosphate near its nicotinamide ring, giving it distinct
electron-transfer properties.
B.In the cell, NADH is usually in excess over NAD+, but NADP+ is usually in excess
over NADPH.
C.NADH is normally involved in anabolic reactions, whereas NADPH is normally
involved in catabolism.
D.Both NADPH and NADH are recognized by the same enzymes with similar
affinities, since the extra phosphate group in NADPH is not involved in such
recognition.
E.In the cell, NADH is found mostly in the form that acts as an oxidizing agent,
whereas NADPH is found mostly in the form that acts as a reducing agent.
The mutation rate in bacteria is about 3 nucleotide changes per 10 billion nucleotides
per cell generation. Under laboratory conditions, bacteria such as Escherichia coli can
divide and double in number about every 40 minutes. If a single Escherichia coli cell is
allowed to exponentially divide for 10 hours in this manner, how many mutations
would you expect to observe on average in the genome (4.5 million nucleotide pairs) of
each of the resulting bacteria compared to the original cell? Assume all mutations are
neutral; that is, they do not affect the cell-division time.
A.Less than 0.001
B.About 0.02
C.One or two
D.About 10
E.About 100
What is the most common additional polymer present in the plant secondary, but not
primary, cell wall?
A.Cellulose
B.Pectin
C.Lignin
D.Starch
Which of the following chromatography methods resembles immunoprecipitation in the
purification of proteins from mixtures?
A.Ion-exchange chromatography
B.Gel-filtration chromatography
C.Hydrophobic interaction chromatography
D.Affinity chromatography
Which of the following is more directly driven by active M-Cdk?
A.Centrosome maturation
B.Centrosome duplication
C.Nuclear envelope reassembly
D.Inactivation of APC/C
E.Cell cleavage
Under which of the following conditions is the Lac operon in Escherichia coli fully
turned on?
A.Low glucose and lactose levels
B.Low glucose but high lactose levels
C.High glucose but low lactose levels
D.High glucose and lactose levels
E.Low cAMP and high glucose levels
Which of the following molecular mechanisms is NOT used in the cell in order to
produce abrupt responses to a signal?
A.Activation of a protein only when bound to multiple molecules of an activating
ligand
B.Activation of a protein only when it is phosphorylated at multiple sites
C.Activation of a protein by simultaneously activating its activator(s) and inactivating
its inhibitors
D.A positive feedback loop in which an activated protein positively regulates its
activator
E.A negative feedback loop in which an activated protein inhibits its activator without
delay
Stimulated B lymphocytes switch from the synthesis of membrane-bound to secreted
antibody molecules by increasing the concentration of a subunit of the trimeric CstF
complex that cleaves and polyadenylates mRNAs. How does this up-regulation of CstF
bring about the production of soluble antibodies?
A.It favors a strong polyadenylation site in the immunoglobulin primary transcript,
creating a longer antibody molecule that is secreted.
B.It activates a weak polyadenylation site in the immunoglobulin primary transcript and
prevents splicing, creating a shorter molecule that is secreted.
C.It favors a strong polyadenylation site in the immunoglobulin primary transcript,
creating a shorter antibody molecule that is secreted.
D.It activates a weak polyadenylation site in the immunoglobulin primary transcript,
creating a longer antibody molecule that is secreted.
E.It favors a strong polyadenylation site in the immunoglobulin primary transcript,
aborting translation and creating a shorter antibody molecule that is secreted.
Protein secondary structure elements such as ± helices and sheets constitute the
major regular folding patterns in proteins. With regard to these elements, ___
A.hydrogen-bonding between the amino acid side chains defines the type of secondary
structure.
B.a certain short amino acid sequence always adopts the same secondary structure.
C.only a few specific amino acid sequences can adopt these repetitive structures.
D.the folding patterns result from hydrogen-bonding between the N-H and C=O groups
in the polypeptide backbone.
E.All of the above.
Indicate whether each of the following descriptions better applies to t-SNAREs (T) or
v-SNAREs (V). Your answer would be a three-letter string composed of letters T and V
only, e.g. TVV.
( )They are usually located on the target membrane.
( )They are composed of a single polypeptide chain.
( )They are usually associated with inhibitory proteins that can be released by Rab
proteins.
Indicate whether each of the following descriptions better matches the rough (R) or the
smooth (S) endoplasmic reticulum (ER). Your answer would be a five-letter string
composed of letters R and S only, e.g. SRSRR.
( )It mostly has a tubular appearance.
( )It contains the transitional ER.
( )It is coated by ribosomes.
( )It can be specialized for functions such as detoxification and lipid metabolism.
( )Sarcoplasmic reticulum in muscle cells is one of its specialized forms.
Indicate true (T) and false (F) statements below regarding light and light microscopy.
Your answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( )Two light waves of the same amplitude and frequency will completely cancel each
other out if not perfectly in phase.
( )If the refractive index of a medium is 1.1, light travels in a vacuum 1.1 times faster
than it does in the medium.
( )The limit of resolution for conventional light microscopy is approximately 0.4 ,
corresponding to the wavelength of violet light.
( )A light-emitting particle can be detected with a light microscope even if it is several
times smaller than the resolution limit of the microscope.
From left to right, indicate whether the transmitter-gated channels for (1) calcium, (2)
chloride, (3) potassium, and (4) sodium at a chemical synapse usually open in response
to excitatory (E) or inhibitory (I) neurotransmitters. Your answer would be a four-letter
string composed of letters E and I only, e.g. EEIE.
Indicate true (T) and false (F) statements below regarding animal development. Your
answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( )A fertilized egg is totipotent.
( )Differences in their regulatory DNA can largely explain the differences between
animal species.
( )Inductive signaling is mostly mediated through G-protein-coupled receptors.
( )A cell’s response to a signal depends on its exposure to other signals at that present
time as well as in the past.
Which of the following graphs better represents the change in the relative conductance
of Na+ and K+ channels during an action potential in a neuronal membrane?
Consider the following three diseases associated with activation-induced deaminase
(AID) and indicate whether you think each of them is accompanied by a higher (H) or
lower (L) AID activity in the affected cells compared to normal cells. Your answer
would be a three-letter string composed of letters H and L only, e.g. LLL.
( )Burkitt’s lymphoma is a cancer of B lymphocytes originating from the germinal
center. In this cancer, chromosomal translocations are observed between the
immunoglobulin heavy-chain genes and proto-oncogenes (genes whose overexpression
can promote cancer), resulting in aberrant expression of the latter.
( )Diffuse large B cell lymphoma is a cancer of B lymphocytes in which, in addition to
chromosomal translocations, high mutation rates are observed in many genes including
proto-oncogenes.
( )Hyper IgM syndrome is a genetic immunodeficiency syndrome in which IgM
antibodies are produced by B cells at high levels and for extended periods, while levels
of IgA, IgE, and IgG antibodies are abnormally reduced.