Deck 5: Fourth Week: Forming the Embryo

Question 1

A researcher knocks out a gene that is expressed in the mouse embryo during neurulation stages,but this gene is never expressed in the neuroepithelium (neural plate or neural tube).Hence,she is surprised when the resulting embryos form neural tube defects.What is the explanation for this?

A) All forces for neurulation are generated within the neural plate.
B) All forces for neurulation are generated in non-neural plate tissues.
C) Forces for neurulation are generated in both the neural plate and in surrounding tissues.
D) Neural tube defects are secondary to abnormal body folding, and the gene is likely expressed in the body folds.
E) Neural tube defects are not the result of gene activity, as they occur randomly regardless of where the knocked out gene is expressed.

Answer 1

C

Question 2

A researcher ablates (removes)the neural folds of an animal embryo prior to formation of neural crest cells.What structure might not develop depending on the exact level removed?

A) Notochord
B) Somite
C) Body wall
D) Parasympathetic ganglia
E) Primitive streak

Answer 2

D

Question 3

A researcher inactivates a gene that affects the dorsal-ventral patterning of the neural tube.Which gene product is known to play such a role?

A) Notch
B) Neurogenin
C) Shh
D) Pdgf
E) Vegf

Answer 3

C

Question 4

A researcher overexpresses the transcription factor Slug in the surface ectoderm.What change in the ectodermal cells would this overexpression cause?

A) The cells would be expected to die.
B) The cells would be expected to undergo convergent extension.
C) The cells would be expected to undergo mitosis.
D) The cells would be expected to undergo meiosis.
E) The cells would be expected to undergo apical constriction.
F) The cells would be expected to undergo an epithelial-to-mesenchymal transformation.

Question 5

Omphalocele and gastroschisis are examples of which type of birth defect?

A) Anterior body wall defect
B) Neural tube defect
C) Urorectal septum defect
D) Buccopharyngeal membrane defect
E) Cloacal membrane defect

Question 6

A researcher overexpresses the actin-binding protein Shroom in the surface ectoderm.What change in the ectodermal cells would this overexpression cause?

A) The cells would be expected to die.
B) The cells would be expected to undergo convergent extension.
C) The cells would be expected to undergo mitosis.
D) The cells would be expected to undergo meiosis.
E) The cells would be expected to undergo apical constriction.
F) The cells would be expected to undergo an epithelial-to-mesenchymal transformation.

Question 7

A woman has a child with spina bifida aperta.She is planning to have another child and is concerned that the second child will also have spina bifida aperta.What should her physician advise her to take daily to reduce the chances that the second child will have spina bifida aperta?

A) Aspirin
B) Warfarin
C) Accutane
D) Folic acid
E) Calcium supplements

Question 8

A major tissue movement involved in neurulation is convergent extension.What signaling pathway plays an essential role in convergent extension?

A) Fgf
B) Tgfbeta
C) Notch-Delta
D) Wnt
E) Ephrin-Eph

Question 9

The inner tube of the tube-within-a-tube body plan gives rise to which structure?

A) Heart tube
B) Neural tube
C) Otocyst
D) Gut tube
E) Somitocele

Question 10

A first-year surgery resident sees a child with a skin-covered neural tube defect.The chief resident says that the defect was caused by abnormal secondary neurulation.Assuming this is true,at what level of the CNS would the defect occur?

A) Brain
B) Upper cervical spinal cord
C) Lower cervical spinal cord
D) Upper thoracic spinal cord
E) Lower thoracic spinal cord
F) Lumbosacral and/or coccygeal spinal cord