BICD 130 wi07 midterm

BICD 130 wi07 midterm - BICD 130 Embryos, Genes, and...

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BICD 130 — Embryos, Genes, and Development Winter 2007 Midterm Exam (Four parts, 100 points total) ______________________________________________________ Please PRINT your name here Please write your answers in ink . Requests for regrades will not be considered for exams done in pencil. Part I (15 pts.)___________________________ Part II (54 pts.)___________________________ Part III (21 pts.)__________________________ Part IV (10 pts.)___________________________ "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." --Lewis Wolpert
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I. (15 pts.) The diagrams above show three stages of chick embryo development: gastrulation (top), early neurulation (middle), and late neurulation (bottom). Fill in the 15 blank lines with the names of the indicated structures or tissues. Be careful to give the name that is appropriate to the stage of development shown.
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1. Hensen’s Node 2. Primitive groove/streak 3. Epiblast, Ectoderm 4. Blastocoel 5. Hypoblast 6. Endoderm 7. Mesodermal cells/mesenchyme 8. Ectoderm 9. Neural groove/neural plate (MHP cells ok, primitive groove IS NOT) 10. Endoderm 11. Notochord 12. Mesoderm 13. Dorsal ectoderm/presumptive epidermis 14. Neural tube 15. Neural crest cells
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II. (54 pts.) 1. (7 pts.) In the nematode worm C. elegans , netrin protein encoded by the unc-6 gene acts as an axon guidance molecule. Netrin expressed in ventral cells is attractive to the axons of sensory neurons (which project ventrally from laterally located cell bodies) but repulsive to the axons of motor neurons (which project dorsally from ventrally located cell bodies). Draw diagrams illustrating the sensory and motor axon patterns in (a) a wild-type worm; (b) an unc-6 mutant; (c) a mutant for unc-40 , which encodes a component of an attractive netrin receptor; (d) a mutant for unc-5 , which encodes a component of a repulsive netrin receptor. -1 point for no orientation; No credit if no labeling of axons a) 1 point b) 2 points unc-6 mutant Sensory Motor No migration of either Neuron Neuron neuron type c) 2 points unc-40 mutant d) 2 points unc-5 mutant No migration of No migration of sensory neurons motor neurons 2. (10 pts.) Describe in detail how, after the completion of neurulation, two signaling centers pattern the neural tube in the D/V axis. Include in your answer the original sources of the two signals, the signaling molecules involved, and the effects of the signals on the neural tube. Use diagrams to illustrate your answer.
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3. (8 pts.)
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BICD 130 wi07 midterm - BICD 130 Embryos, Genes, and...

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