E55-2010 exam 2

A over time what behavior do you expect to see in the

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A. Over time, what behavior do you expect to see in the mixed mass of cells? Explain in a short phrase or 1 sentence. B. What term is used to describe this behavior? ______________________________________________________ C. What is the molecular basis for this behavior? Explain in 1-2 sentences. D. Name two other mechanisms that can drive cell movements during gastrulation. __________________________________________ __________________________________________ 26. (6 points, 2 points each) Match the following cell types from gastrula-stage sea urchin embryos (left column) with the correct type of morphogenetic movement (top right column). Use only one response from the right for each cell type. However, some morphogenetic movements may be used more than once or not at all. MOVEMENT: A. convergent extension B. delamination C. ingression D. involution E. invagination F. epiboly CELL TYPES: Primary mesenchyme _________________________________ Archenteron cells as archenteron elongates__________________ Vegetal plate cells after primary mesenchyme departs_________
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E-55, Exam 2-2010: Name Page 8 of 8 27. (8 points, parts A-B 2 points each, part C worth 4 points) In a classic experiment performed by Spemann and colleagues, a baby hair was used to separate the amphibian zygote into two halves, such that (A) both halves received some gray crescent or (B) only one half received the gray crescent. The outcome of this experiment suggests that inheritance of the gray crescent may be vital for dorsal structures. A. What signaling center is formed by cells that descend from the gray crescent? ______________________________________ B. What function does this signaling center perform? Briefly state in a short phrase or 1 sentence. C. If you were to remove gray crescent cytoplasm from a donor embryo, and microinject it into a 2-cell stage host embryo (injecting it into the blastomere without gray crescent, such that the host now has mirror-image gray crescent cytoplasm areas), what would happen to the embryo? Predict the phenotype in a short phrase or 1 sentence. 27. (6 points) In a classic episode of the X-files entitled “Postmodern Prometheus,” an evil developmental biologist is experimenting with a human Hox gene most similar to the Drosophila homeotic gene proboscipedia . Mulder is unfamiliar with homeotic genes, and asks for an explanation from Scully, who does her best to remember her undergraduate biology classes. Name three key features of homeotic genes that Scully should enumerate to Mulder: Feature #1:_______________________________________________________________ Feature #2:_______________________________________________________________ Feature #3:_______________________________________________________________
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A Over time what behavior do you expect to see in the mixed...

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