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Return to Principles of Development 6e Student Resources
Chapter 5 Self-test questions
Vertebrate development III: Chick and mouse - completing the body plan
Somites will give rise to
heart and blood
internal organs of the abdomen
the vertebral column and skeletal muscles
the spinal cord.
Vg-1 and Wnts are used in both frog and chick embryos to establish a body axis, although in chick this is the antero-posterior axis instead of the dorso-ventral axis. What is the region of the chick embryo that is analogous to the Nieuwkoop center in frog embryos?
posterior marginal zone
The positioning of the dorso-ventral axis in
is determined by _____, while the positioning of the antero-posterior axis in chicks is determined by _____.
gravity; point of sperm entry
maternal factors in both cases
position in the egg chamber; gravity
the point of sperm entry; gravity.
At the morula stage during mammalian embryonic development, the 'outer' cells, which will form trophectoderm, express ________; whereas 'inner' cells, which will form inner cell mass, express ________.
The central nervous system is derived from _____, the axial skeleton is derived from _____, and the muscles of the trunk are derived from _____?
ectoderm, mesoderm, endoderm
mesoderm, endoderm, endoderm
ectoderm, mesoderm, mesoderm
all are derived from mesoderm
What would be the effect on the timing of somite formation, if a piece of the pre-somitic mesoderm of a chick embryo is rotated by 180° and reinserted in its original position?
there would be no effect because the embryo would regulate and development would proceed normally
antero-posterior development would be blocked at that point, and more posterior structures would fail to form
the rotated mesoderm will reverse the gradient of somite formation, so that somite formation posterior to the rotated mesoderm will begin in the posterior and move forward to meet the previously formed somites
the timing of somite formation will be reversed in the rotated block only, proceeding from posterior to anterior, but the rest of the somites will form in a normal fashion, proceeding from anterior to posterior
Relative to the primitive streak and Henson's node, somite formation in the chick embryo occurs
Anterior to Henson's node, after the primitive steak has retracted past that point.
Posterior to Henson's node, as cells from the lateral portions of the epiblast move in through the primitive streak to become mesoderm.
Adjacent to Henson's node, as the primitive streak migrates toward the anterior of the embryo.
Somite formation occurs simultaneously along the axis, after Henson's node has fully retracted.
What observation suggests that positional values along the antero-posterior axis are specified in the pre-somitic mesoderm before somite formation begins?
A number of genes have a cyclic pattern of expression in the pre-somitic mesoderm
Somites in the anterior of the embryo form before somites in the more posterior regions.
A graft of a portion of pre-somitic mesoderm to another level on the axis will develop into structures typical of its original position.
The FGF gradient drops off in the region that is forming somites.
What is the initial signal that causes cells in the pre-somitic mesoderm to condense into somites?
High level of retinoic acid signaling.
Low level of FGF/Wnt signaling.
Expression of different Hox gene combinations along the antero-posterior axis of the embryo.
encode transcription factors that specify a position along the anterior-posterior axis in vertebrates
encode signaling molecules used during somite formation
control the formation of vertebrae in mice, but are not found in other animals
are expressed only in the mesoderm
The effect of grafting an extra piece of notochord into a dorsal position adjacent to pre-somitic mesoderm is
the pre-somitic mesoderm will degenerate
somites will form but fail to differentiate
signals from the notochord will convert presumptive dermomyotome into sclerotome
the somite will be converted almost entirely to muscle-forming cells
The use of segments as a developmental strategy in vertebrates is evident in
the axial skeleton, only
the hindbrain, only
both the axial skeleton and the hindbrain
Although the vertebrate body plan outwardly displays a mirror-image symmetry with regard to left and right, the internal organs are not symmetrical. How does this left-right asymmetry develop?
The two cells of the Nieuwkoop center signal each other and become either left or right.
Maternal factors that determine left and right are packaged into the egg, just as dorsalizing factors are.
Differential release of Ca
ions on the left side leads to expression of Nodal and Pitx2 on the left.
No special mechanism is required, since the formation of an antero-posterior axis and a dorso-ventral axis automatically determines left and right.
Which of the following is NOT involved in left-right asymmetry of vertebrates?
Epidermal growth factor
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