#Question id: 7250
#Unit 5. Developmental Biology
Following
statements are regarding to signals that regulate axis extension in chick
embryos.
A.
In the stage 10 chick embryo, Fgf8 inhibits expression of the retinoic acid
(RA) synthesizing enzyme Raldh2 in the presomitic mesoderm and the expression
of the RA receptor RARβ in the neural ectoderm, thus preventing RA from
triggering differentiation in the caudal-lateral epiblast cells and the
caudal-most paraxial mesoderm.
B.
Fgf8 inhibits Sonic hedgehog (Shh) expression in the neural tube floorplate,
controlling the onset of ventral patterning genes.
C.
FGF signaling is also required for expression of Delta1 in the medial portion
of the caudal-lateral epiblast cells and promotes expression of Wnt8c.
D.
Fgf8 decays in the caudal paraxial mesoderm, Wnt signaling, most likely
provided by Wnt8c, now acts to promote Raldh2 in the adjacent paraxial mesoderm.
RA produced by Raldh2 activity expresses Fgf8 and Wnt8c.
Which of the following statements are correct?
#Question id: 7251
#Unit 5. Developmental Biology
Following statements are regarding to the three “toggle switches” activated
along the anterior-posterior axis to establish gap gene domains in drosophila.
A.
The mutual inhibition of Knirps and Hunchback positions the Knirps protein
domain at around 60–80% along the anterior-posterior axis.
B.
Hunchback inhibits Krüppel expression at high concentrations but promotes it at
intermediate concentrations.
C.
Hunchback inhibits Krüppel expression at intermediate concentrations but
promotes it at high concentrations.
D.
Krüppel and Giant mutually inhibit each other’s synthesis.
E.
Kruppel inhibits Giant expression at high concentrations but promotes it at
intermediate concentrations.
Which of the following statements are correct?
#Question id: 7252
#Unit 5. Developmental Biology
Although some species differences exist, the process of primary neurulation is relatively similar in all vertebrates. Primary neurulation can be divided into four distinct but spatially and temporally overlapping stages:
A. Bending of the neural plate
B. Closure of the neural tubeC. Elongation and folding of the neural plate
D. Convergence of the neural folds
C. Elongation and folding of the neural plate
D. Convergence of the neural folds
What is the correct sequence?
#Question id: 7253
#Unit 5. Developmental Biology
In drosophila, the segment polarity genes encode proteins that are constituents of the Wnt and Hedgehog signaling pathways. Which of the following is correct regarding to model for transcription of the segment polarity genes engrailed (en) and wingless (wg).
#Question id: 7254
#Unit 5. Developmental Biology
Following statements regarding to the micromeres specification and regulatory input in sea urchin embryo. Which of the following statement is correct?
#Question id: 7255
#Unit 5. Developmental Biology
The
hypostome acted as an “organizer” of the hydra. This notion has been confirmed
by:
A.
when transplanted, the hypostome can induce host tissue to form a second body
axis.
B.
the hypostome do not produces the head inhibition signal.
C.
the hypostome is the only “self-differentiating” region of the hydra.
D.
the hypostome produces a “head activation signal” that suppresses the formation
of new organizing centers.
Which one of the following combinations are incorrect?