In the following fate map for the Xenopus blastula, indicate which zone in the map (A
to D) better corresponds to each of the following fates. Your answer would be a
four-letter string composed of letters A to D only, e.g. DCAB.
( )Lung
( )Blood
( )Brain
( )Skin
Which of the following cell junctions uses cadherin cell adhesion molecules to anchor
the actin cytoskeleton?
A.Tight junction
B.Adherens junction
C.Desmosome
D.Hemidesmosome
E.Gap junction
F-actin is not a straight polymer but can be considered a double-helical assembly. The
two protofilaments twist around each other and cross over approximately every 13 actin
subunits, and the subunits in each protofilament are repeated every 2.8 nm along the
helix. F-actin is almost 8 nm wide. Different myosin motors have different ‘step
lengths” on actin depending on their function. Which of the following step lengths
would you expect to belong to a processive myosin motor that carries large cellular
cargoes such as endocytic vesicles?
A.About 2.8 nm
B.About 8 nm
C.About 13 nm
D.About 27 nm
E.About 36 nm
Which of the following is NOT true regarding cell-type specification in developing
animals?
A.Members of the MyoD/myogenin family of transcription regulators drive cells to
differentiate into muscle cells.
B.Members of the Achaete/Scute family of transcription regulators drive the cells to
form endothelial layers.
C.Many proteins that induce the differentiation of particular cell types belong to the
bHLH (basic helix-loop-helix) class of transcription regulators.
D.Eyeless is both necessary and sufficient to generate eye structures composed of
various specialized cell types in Drosophila.
E.In vertebrates, loss of the Eyeless homolog Pax6 leads to an animal without eyes.
Blood platelets in an adult human …
A.are made in lymphoid organs.
B.are NOT derived from hematopoietic stem cells.
C.lack nuclei.
D.All of the above.
In meiosis, a crossover in one position is thought to inhibit crossing-over in the
neighboring regions. This regulatory mechanism ___
A.results in a very uneven distribution of crossover points along each chromosome.
B.ensures that even small chromosomes undergo at least one crossover.
C.controls how the Holliday junctions are resolved.
D.All of the above.
Consider a transcription regulatory protein (A) that can bind to the promoter (p) of a
target gene. 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. What is the slope of the curve at time zero?
A.2 koff
B.2 kon
C.5 koff
D.5 kon
E.9 koff
Eukaryotic pre-mRNAs undergo a number of modifications such as capping at the 5′
end. A 5′ cap___
A.consists of a modified terminal adenine nucleotide.
B.has a 3′-to-5′ linkage between the terminal nucleotide and the 5′ end of the
pre-mRNA.
C.contains a triphosphate bridge between the terminal base and the 5′ end of the
pre-mRNA.
D.carries a negative charge in the terminal base due to methylation.
E.is identical for all mRNAs that are transcribed by RNA polymerase II.
Initiator and executioner caspases share all of the following features EXCEPT that …
A.they are cysteine proteases (they have a cysteine residue at their active site).
B.their inactive form is a monomer.
C.they undergo cleavage during activation.
D.their active form is a dimer.
E.they are inhibited by IAPs.
Based on the variation of genome size and gene number in the organisms presented in
the following graph, which organism has the highest number of genes per unit length of
their genome? (Note the logarithmic scale.)
A.H. sapiens
B.M. musculus
C.A. thaliana
D.C. elegans
E.E. coli
You have used a reporter gene system to investigate the contribution to gene expression
of three cis-regulatory DNA sequences (A to C) from a key developmental gene.
Reporter gene expression from constructs containing all three or only a subset of the
regulatory sequences is summarized in the diagram below. According to these findings,
indicate whether each of the following conclusions is (Y) or is not (N) acceptable. Your
answer would be a four-letter string composed of letters Y and N only, e.g. NNNN.
( )Region B is likely to normally bind an activator and turn the gene on.
( )Region C is sufficient for activation of gene expression.
( )Region A is necessary for activation of gene expression.
( )Region C is necessary for activation of gene expression.
Indicate true (T) and false (F) statements below regarding gene control. Your answer
would be a four-letter string composed of letters T and F only, e.g. TTFT.
( )Development of multicellular organisms from a fertilized egg only rarely involves
DNA rearrangements in specialized cells.
( )A typical human cell expresses less than 1% of its approximately 30,000 genes at any
given time.
( )Genes that are expressed in all cell types usually vary in their level of expression in
different cell types.
( )Many differentiated plant cells can be fully de-differentiated and give rise to an entire
plant.
Reference: Contractile-Ring Positioning
Three models for contractile-ring positioning in animal cells are presented in the
schematic diagrams below. Answer the following question(s) according to these models.
In experiments on the flattened eggs of the sea urchin Tripneustes gratilla, cytokinesis
was analyzed after placing a small physical barrier (e.g. a glass needle or an oil droplet)
between the spindle and various areas of the cell cortex. Blocks that were located over
the equatorial plane prevented furrow formation in the proximal membrane, whereas
blocks located in other areas did not affect furrowing. Which model (1 to 3) is NOT
supported by these results? Write down 1, 2, or 3 as your answer.
Indicate whether each of the following descriptions better applies to a centromere (C), a
telomere (T), or an origin of replication (O). Your answer would be a seven-letter string
composed of letters C, T, and O only, e.g. TTTCCTO.
( )It contains repeated sequences at the ends of the chromosomes.
( )It is NOT generally longer in higher organisms compared to yeast.
( )Each eukaryotic chromosome has many such sequences.
( )There are normally two such sequences in each eukaryotic chromosomal DNA
molecule.
( )There is normally one such sequence per eukaryotic chromosomal DNA molecule.
( )It is where DNA duplication starts in S phase.
( )It attaches the chromosome to the mitotic spindle via the kinetochore structure.
When unfolded proteins accumulate in the lumen of the endoplasmic reticulum due to
inefficient folding conditions, a membrane-bound protein kinase is activated and
phosphorylates a subunit of the translation initiation factor eIF2. Indicate which of the
following events would (Y) or would not (N) occur as a result. Your answer would be a
four-letter string composed of letters Y and N only, e.g. YYYY.
( )eIF2 binds tightly to the ribosome.
( )Translation initiation is stimulated.
( )The GDP-bound form of eIF2 accumulates.
( )eIF2B is activated.