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A centrolecithal mesolecithal b isolecithal

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A. centrolecithal, mesolecithal B. isolecithal, mesolecithal C. mesolecithal, mesolecithal D. telolecithal, centrolecithal E. isolecithal, isolecithal ______20. Nodal signals induce mesoderm across the D-V axis in the frog, and a range of Nodal signal intensities are triggered by: A. maternal deposits of VegT alone B. maternal deposits of B-catenin alone C. zygotic production of VegT D. a combination of B and C E. a combination of A and B that is altered after successful fertilization
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E-55, Exam 2-2010: Name Page 5 of 8 Short answer (point values indicated). Provide a concise response in the space provided. 21. (10 points, 2 points each) Axis specification is an important event during early embryogenesis. A. In the fly, which axis is established first? Circle your response: A-P D-V L-R B. In the fly, name the protein that the oocyte produces that is essential for setting up both the A-P and D-V axes? __________________________________________ C. If you were to prevent microtubule polymerization in the fly oocyte, which axis or axes would be specified? Justify your response in 1-2 sentences. D. In the frog, which axis is established first? Circle your response: A-P D-V L-R E. If you were to prevent microtubule polymerization in the frog zygote, what phenotype would result? (Hint: we are looking for the one-word description of phenotype) __________________________________________ 22. (6 points) A 1-cell stage frog zygote is incubated with a drug that degrades B- catenin molecules. 1. Will the embryo be able to produce ventral tissues? Circle your response: yes no 2. Will the embryo be able to produce neural tissues? Circle your response: yes no 3. Will the embryo be able to make an organizer? Circle your response: yes no
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E-55, Exam 2-2010: Name Page 6 of 8 23. (10 points, 2 points each) During early cleavage, a period of extremely rapid cell division occurs in most vertebrate embryos. A. What stages of the cell cycle occur during the rapid cell division period? ______________________________________________ B. What are the two molecular components of the MPF complex? 1 ________________________________________ 2 ________________________________________ C. Which of the molecular components is degraded with each cell cycle? ________________________________________________ After the rapid period of cell division, there is a switch to a slower period of cleavage cell division. What name is given to this switch, and what new molecular event commences in each cell at the time of this switch?
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