Exam 3 Flashcards
The morphology of specific muscles within the limb buds is determined by which of the following factors? A. Surrounding connective tissue B. BMPs C. Apical ectodermal ridge D. Noggin
A. Surrounding connective tissue
Pre-muscle cells in the developing limb bud are derived from which of the following sources? A. Lateral plate mesoderm B. Somitic dermatomes C. Somitic myotomes D. Neural crest
C. Somitic myotomes
Which of the following represents the principle function of the AER?
A. Stimulating outgrowth of the limb bud
B. Setting up the AP axis of the limb bud
C. Determining the specific characteristics of the ectodermal appendages of the limb
D. Determining the pattern of neural outgrowth of the limb.
A. Stimulating outgrowth of the limb bud
If the limb disc of a salamander embryo is rotated 180 degrees, so that both the AP and the DV axes are reversed, which of the following would be observed?
A. The resulting limb would be completely normal with no reversal of axes
B. The AP axis of the resulting limb would be reversed, but not the DV axis
C. The DV axis would be reversed but not the AP axis
D. Both axes would be reversed
B. The AP axis of the resulting limb would be reversed, but not the DV axis
Numerous experiments have shown that retinoic acid is capable of inducing the formation of the posterior limb in vertebrates. Retinoic acid is not the actual morphogenetic but is capable of activating which of the following genes, which is thought to express the actual morphogen? A. Shh gene B. Wnt-7 gene C. Pax-3 gene D. Noggin gene
A. Shh gene
Pattern formation along the proximodistal axis of the limb bud is primarily determined by which of the following? A. Paxa gene B. Hoxd gene C. Retinoic acid D. Shh
B. Hoxd gene
The presence of webbing between the toes of wading birds such as ducks and the presence of webbed fingers (syndactyly) is most likely associated with which of the following? A. Over expression of the Noggin B. Oligohydramnios C. Reduced apoptotic activity D. Amniocentesis
C. Reduced apoptotic activity
Which of the following experiments carried out on salamander embryos illustrates the developing limb is a highly regulative system?
A. Split a limb primordium into two halves and prevent them from fusing
B. Juxtapose two equivalent halves of a limb primordium
C. Remove part of a limb primordium
D. All of the above
D. All of the above
Which of the following factors functions as the initial initiator of future hindlimb development? A. Hoxd B. Tbx4 C. Shh D. Gli3
B. Tbx4
In limb development, the attraction of the outgrowing nerves to peripheral organs seems to be unspecific to a very high degree. Connections between a nerve and the end organ can be made only if the two correspond to each other. These assumptions are based on which of the following experiments?
A. An eye was transplanted to the side of the salamander embryo after the forelimb rudiment was removed
B. A salamander forelimb bud was removed and replaced by a hindlimb bud
C. A salamander limb rudiment was transplanted to the flank of a host salamander
D. An obstacle was placed between the spinal cord and the region where the hindlimb rudiment was to develop in a salamander embryo
A. An eye was transplanted to the side of the salamander embryo after the forelimb rudiment was removed
During limb development, pre-muscle cells in the somite express c-met, which is the receptor for which of the following? A. Pax-3 B. N-cadherin C. Tcf-4 D. Scatter factor
D. Scatter factor
In the formation of limb joints, which of the following signal molecules is responsible for inhibiting BMP in the region of the future joint cavity? A. Shh B. Noggin C. Wnt-1 D. Eng-1
B. Noggin
Which of the following occurs when an additional limb bud is transplanted into the immediate vicinity of the host forelimb of a salamander embryo?
A. Neither limb bud will be supplied be any branches of the brachial plexus
B. The brachial nerves will develop branches running out to the additional limb and will supply it
C. The transplanted limb bud will be supplied by local nerves that would normally supply flank muscles
D. Local brachial plexus nerves deviate from the normal limb bud and supply only the transplanted limb bud
B. The brachial nerves will develop branches running out to the additional limb and will supply it
The formation of club foot (talipes equinovarus) is associated with which of the following?
A. A misplaced ZPA
B. Defective cellular migration from somites
C. Thalidomide
D. Oligohydramnios
E. A neural crest defect
D. Oligohydramnios
Which of the following is observed when the forelimb rudiment of a salamander embryo is removed so that the limb fails to develop?
A. The associated spinal ganglia increase to more 150%of their normal size
B. Local nerves are not affected
C. The nerves of the brachial plexus remain smaller (thinner) than they would have been if the limb were still there
D. Nerves of the future brachial plexus undergo apoptosis
C. The nerves of the brachial plexus remain smaller (thinner) than they would have been if the limb were still there
