%20Exam1_key_08 - EXAM 1 -_KEY Developmental Neurobiology,...

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Host Embryo Donor Embryo Grafted Embryo Donor Derived Spemann Organizer Cut Out Small Region Graft Into Host Spemann Organizer Emits Signals EXAM 1 -_KEY Developmental Neurobiology, BIPN144 April 24, 2008 100 Points Total Question TA 1 Afsoon 2 Susan B. 3 Sue Z. 4 Alex 5 Keith 20 pts. 1. What two criteria must a molecule meet to be considered a morphogen? 5 pts. 1) Factor is present in graded concentration 5 pts. 2) Factor elicits different responses at different concentrations Give one example of a morphogen. 4 pts. Example of morphogen: Dorsal: Describe briefly how this molecule meets the defining criteria for being a morphogen. 3 pts. 1) It is present at higher levels in the ventral region (mesoderm) than in the lateral region (neuroectoderm) 3 pts. 2) It activates expression of snail and twist at high levels in mesoderm and rho and sog at lower levels in the neuroectoderm. 20 pts. 2. Hilde Mangold provided the first clear evidence for the existence of a secreted factor which could redirect the fates of cells in the frog embryo. Draw a diagram of the Mangold experiment indicating how she performed her transplantation experiment and what the result of that experiment was. Distinguish host and donor derived tissues in your diagram.
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%20Exam1_key_08 - EXAM 1 -_KEY Developmental Neurobiology,...

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