February 19, 1992 TIME: 50 minutes

TOTAL POINTS: 60

(VALUE) QUESTION

(20) 1. Describe the origin of inositoltrisphosphate in the fertilized sea urchin egg and its function in the activation of development. Cite evidence that supports the function you have ascribed to it.

(30) 2. Provide clear definitions of the following terms:

(25) 3. When is the ZP-3 gene expressed, and how is its expression regulated? Cite experimental evidence to support your answer.

(25) 4. How is the embryonic axis established in Xenopus? Cite experimental evidence to support your answer.