Please answer the following: 4. Discuss how axis formation occurs in amphibian d
ID: 264668 • Letter: P
Question
Please answer the following:
4. Discuss how axis formation occurs in amphibian development by answering each of the following questions.
a. What are the key molecular and cellular events that lead to the formation of the gray crescent?
b. How does the convergence of multiple signal pathways due to the formation of the gray crescent lead to the formation of the primary organizer in Amphibians? Describe these pathways, the key molecules they effect, and how they lead to the primary organizer forming opposite the site of sperm entry.
c. What are the properties of the primary organizer?
d. What cellular events lead to the formation of different germ layers during gastrulation in amphibians. Discuss the role and function of superficial and deep cells, bottle cells, the blastocoel, the blastopore lip, the IMZ, the NIMZ, the archenteron, mediolateral intercalation, convergent extension, the yolk plug, and epiboly.
e. In the cellular context you describe in (d), how do gradients of paracrine signals contribute to the formation of the A/P and D/V axis? Describe the paracrine signals and the functional contributions of each. f. Classic experimental work led to the idea that underlying mesodermal tissue induces the formation of the neural ectoderm.
i. What experiments demonstrated that this type of induction occurs?
ii. What is our current understanding of the basis of this inductive process?
iii. More generally, what insights has this understanding, as well as our understanding of how stem-cell niches are regulated, provided about how multiple paracrine signals are used to influence developmental processes?
Explanation / Answer
Please answer the following: 4. Discuss how axis formation occurs in amphibian d