If mice are injected with antibodies against selectin homing receptors or against the
integrin ligand I-CAM1 (which is expressed on the surface of endothelial cells), they
show immune defects, such as higher susceptibility to bacterial infections. Which of the
following properties of lymphocytes at endothelial cells would you expect to observe
after injection with both antibodies?
A.Normal lymphocyte rolling and normal lymphocyte adhesion
B.Impaired lymphocyte rolling but normal lymphocyte adhesion
C.Normal lymphocyte rolling but impaired lymphocyte adhesion
D.Impaired lymphocyte rolling and impaired lymphocyte adhesion
The following graph qualitatively represents the gradients of Nodal and Lefty gene
products in an early frog embryo. The position along which primary axis is defined by
these gradients? Which curves correspond to these two proteins?
A.D-V axis; curves 1 and 2
B.D-V axis; curves 1 and 3
C.A-V axis; curves 1 and 2
D.A-V axis; curves 1 and 3
Stable -sheet aggregates can form from many proteins, forming intertwined cross-beta
strands that have the potential to kill cells or damage tissues. Which of the following is
NOT true regarding these aggregates?
A.They form almost exclusively in the cells of the nervous system.
B.Different types of such aggregates can form from the same protein.
C.Their formation is associated with conditions such as Parkinson’s disease and Kuru.
D.They can form spontaneously, but also can be triggered to form by an infection with
the same aggregate.
E.Some healthy cells form these aggregates to store their secretory proteins.
The number of ways in which protein domains fold in nature is limited. Which of the
following is a better estimate of this number?
A.200
B.2000
C.200,000
D.2,000,000
E.20 million
Which of the following is NOT correct regarding both Cas9 and EcoRI?
A.They are both endonucleases.
B.They both create double-strand breaks in DNA.
C.They both recognize their target sequences with the help of guide RNAs.
D.They are both part of bacterial defense mechanisms against foreign DNA.
E.They are both greatly useful in manipulating DNA and studying gene expression and
function.
Indicate true (T) and false (F) statements below regarding colorectal cancers. Your
answer would be a four-letter string composed of letters T and F only, e.g. TFFF.
( )Observation of polyps in the colon epithelium of a patient is an indication of a
malignant carcinoma.
( )Progression of colorectal cancer is very slow and normally takes over 10 years to turn
into malignancy.
( )Colorectal cancers are usually diagnosed later in life.
( )Invasive colorectal cancer cells usually metastasize to lymph nodes via lymphatic
vessels and then into the bloodstream.
In the following schematic drawing of connexons as seen from the cytosol of a cell,
what is the approximate diameter of each of the pores? Which of the indicated
connexons (1 or 2) is more likely to have been incorporated more recently?
A.About 20 nm; connexon 1
B.About 4 nm; connexon 1
C.About 1.5 nm; connexon 1
D.About 4 nm; connexon 2
E.About 1.5 nm; connexon 2
In which of the following structures are actin-myosin II bundles regulated by the
troponin complex?
A.Stress fiber
B.Circumferential belt
C.Contractile ring
D.Adherens junction
E.None of the above
This complex uses ATP and forms an “isolation chamber” for its misfolded protein
substrates, allowing them to fold to their native conformation. It is called___
A.a proteasome.
B.a ribosome.
C.Mediator.
D.a chaperonin.
E.an exosome.
The three families of cellular macromolecules are polymerized and depolymerized by a
general mechanism involving water. Each of them has a set of monomers whose
polymerization changes the total free energy of the system. Which of the following
statements is true regarding these macromolecules?
A.Each polymerization step requires free-energy input and proceeds by the
consumption of one water molecule.
B.Each depolymerization step requires free-energy input and proceeds by the
consumption of one water molecule.
C.Each polymerization step requires free-energy input and proceeds by the release of
one water molecule.
D.Each depolymerization step requires free-energy input and proceeds by the release of
one water molecule.
In a multicellular organism such as a mammal, loss-of-function mutations in many
genes can contribute to the development of cancer. These genes are therefore called
tumor suppressors. In their absence, the cell fails to stop progression through the cell
cycle under conditions in which normal cells would arrest, paving the way for
tumorigenesis. Indicate whether each of the following proteins is (Y) or is not (N)
expected to be the product of a tumor suppressor gene based on its function in the cell
cycle. Your answer would be a four-letter string composed of letters Y and N only, e.g.
YNNN.
( )Rb
( )Myc
( )p53
( )p21
Indicate whether each of the following descriptions better applies to N-linked (N) or
O-linked (O) glycosylation. Your answer would be a four-letter string composed of
letters N and O only, e.g. OONO.
( )It is abundant in proteoglycans.
( )It involves the attachment of a preassembled block of oligosaccharide onto a protein.
( )It is attached to a serine or threonine residue in the protein.
( )It involves heavily sulfated sugars.
Indicate whether each of the following molecules is an intermediate in glycolysis (G) or
in the tricarboxylic acid cycle (T). Your answer would be a four-letter string composed
of letters G and T only, e.g. GGTT.
( )Fumarate
( )Malate
( )Phosphoenolpyruvate
( )Succinate
Indicate whether you would use a fluorescent organic molecule (O), in situ
hybridization (H), or a coupled fluorescent protein (P) to visualize the cells and their
molecules in each of the following cases. Your answer would be a five-letter string
composed of letters O, H, and P only, e.g. OHOOO.
( )You would like to see where in the early Drosophila embryo the mRNA encoding a
certain transcription regulator is located.
( )You would like to see the nuclei and count them in an early mouse embryo.
( )You would like to visualize chromosome 3 in a human cell culture derived from a
patient’s tissue, based on specific sequences present on this chromosome.
( )You would like to observe the oscillations in Ca2+ ions inside a fertilized frog egg.
( )You would like to compare the localization of two transcription regulatory proteins in
cultured human T cells.
Consider the descriptions below for three different lncRNAs, and determine whether
they function in cis (C) or in trans (T). Your answer would be a three-letter string
composed of letters C and T only, e.g. CCT.
( )The tsiX RNA is transcribed from the X-inactivation center in the X chromosome
that will not be inactivated. It is antisense with respect to Xist, repressing its
transcription and function.
( )The ANRIL lncRNA is an antisense transcript in a gene cluster expressing inhibitors
of cell-cycle proteins. It silences the entire cluster by recruiting heterochromatin
proteins of the Polycomb group.
( )The PTENP1 lncRNA is similar to an mRNA that encodes the protein PTEN, and
contains many of the miRNA response elements present in PTEN mRNA; it therefore
protects the PTEN mRNA from miRNA-mediated silencing by acting as a decoy.