ICQs15,16.ppt

ICQs Class 16 (.5 pts) In the frog embryo, different kinds of mesoderm migrate into the embryo as gastrulation progresses (dorsal, then intermediate, then ventral). What about chick? a. it’s the same b. it’s similar, but there is much more of an A-P gradient c. the mesoderm doesn’t migrate inside during chick gastrulation, but the ectoderm does Epithelial and mesenchymal organization represent two major tissue types in animals. 1. Which of the following statements correctly characterize epithelial or mesenchymal cells? .5 pts Cells are motile. Cells are similar and regular in shape. Cells can communicate with each other through gap junctions. Cells are not in contact, separated by extracellular matrix. i and ii are epithelial, iii and iv are mesenchymal ii, ii, iv are epithelial, iii is mesenchymal i, ii, iii are epithelial, iv is mesenchymal i and iii are epithelial, ii and iv are mesenchymal ii and iii are epithelial, i and iv are mesenchymal ICQs class 15 G 10.5 Xenopus fate map 2. By what embryonic stage are all these fates determined? a. Before fertilization b. At fertilization c. Before gastrulation begins d. By the middle-end of gastrulation e. After gastrulation is complete 3. Which mesodermal precursor cells enter the blastopore first in Xenopus gastrulation? a. presumptive head (anterior) mesoderm b. presumptive tail (posterior) mesoderm. 4. The bottle cells that initiate involution at the blastopore are: (.5 pts) a. presumptive ectodermal cells. b. presumptive mesodermal cells. c. presumptive endodermal cells. 2. Using the figures above, decide why the early isolated animal caps did not make neural cells. Chordin and noggin must be present in the early stage animal cap Chordin and noggin are not present in the early stage animal cap but BMPs are The animal cap cells are initially fated to be epidermis; that fate is changed to neural ectoderm because of inductive events during gastrulation The animal cap cells can no longer be inhibited by BMPs after gastrulation 3. (.5) If you laser-ablated one of the cells (red) beginning to delaminate and form a neuroblast, what is the most likely fate of the cell next to it (indicated with an arrow)? It will become an epidermal cell It will become a neuroblast Its fate is already determined so it doesn’t matter what you do 4. The notochord (chord of cells underlying the neural tube) is composed of Cells from the organizer Cells from the Niewkoop center Ectodermal cells from the animal cap Endodermal cells derived from the bottle cells What would happen if you were to inject N-cadherin into the cells that normally make the surface ectoderm before neurulation? neurulation begins but cannot complete Adhesion molecules play a role in separation of neural tube from overlying epidermis The risk for neural tube defects is two to five times higher than normal if a mother has diabetes. Why? Data pax-3 -/- homozygous mutant mice are born with neural tube defects Diabetic mice have low pax-3 levels pax-3 interacts with p53 (remember the role of p53?) Work with your group to propose a role for how pax-3 and p53 might be involved in neural tube defects Can you draw a pathway? High blood sugar --| Pax-3 --| p53 ? cell death Low pax-3 leads to activated p53 leads to cell death leads to neural tube closure defect Pax-3 and p53 double mutants did not have neural tube defects