1. MCDB 4650 Cell Signaling in Development

2. Why might a cell (cell 1) activate a transcription factor in response to a growth factor binding an RTK while another cell (cell 2) does not? a.cell 2 is lacking the receptor b.cell 1 contains another transcription factor that cell 2 does not have c.cell 2 contains another transcription factor that cell 1 does not have d.all of the above

3. AB Delta (Dl) Notch (N) In a normal embryo, which of the two cells above will become a neuroblast? a. A b. B c. Neither d. Both

4. If an embryo were mutant for Delta (no Delta protein present on either cell above), which cell will become a neuroblast? a. A b. B c. Neither d. Both AB Delta (Dl) Notch (N)

5. Which of the following statements about ligands and receptors is false? a) Components of the extracellular matrix can act as signaling ligands. b) In signaling by steroids, the receptor and the activated transcription factor are the same molecule. c) Juxtacrine signaling involves both membrane-bound ligands and membrane-bound receptors. d) Two different types of cells that carry the same receptor on their surfaces will generally respond in the same way to the ligand that the receptor recognizes.

6. The number of different signaling pathways involved in embryonic development is a) none b) between 5 and 10 c) 10 - 20 d) more than 20

7. In the Hedgehog pathway, "half" of the cleaved Ci target transcription factor acts as a repressor of the same target genes that are activated by the uncleaved Ci protein when Hedgehog is present. The most likely explanation for this, based on not just what's in the figure, but also your knowledge of combinatorial control, is that: a) the cleaved Ci binds to a different response element than the uncleaved Ci. b) the cleaved Ci binds to different additional transcription factors or cofactors than the uncleaved Ci. c) the cleaved Ci does not bind to additional transcription factors or cofactors, whereas the uncleaved Ci does.

8. What can determine how a cell responds to a ligand? a) The receptors and downstream signaling proteins it has synthesized previously. b) The transcription factors, splicing factors, and other mRNA binding proteins it has synthesized previously. c) The presence of other signaling pathways in the cell and ligands in the cell’s vicinity. d) All of the above. e) All but one of (a), (b), and (c).

9. Blastula-stage animal caps incubated in Ca++, Mg++ free medium containing EDTA (a chelating agent) could be easily disaggregated into individual cells because: a) lowering cation concentrations induces shape changes in the blastomeres so that they pull apart. b) integrin molecules that hold cells together require Mg++ to bind to each other. c) cadherin molecules that hold cells together require Ca++ to bind to each other. d) Ca++ and Mg++ are required for the association of cadherins with integrins that hold cells together.

10. Match each ligand or receptor from the list below with the type of signaling in which it participates: (1) juxtacrine, (2) paracrine, or (3) endocrine. a) Receptor tyrosine kinases b) Wnt c) Notch d) Hedgehog e) Testosterone