Exam 2 ID#: November 9, 2006

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1 Biology 4361 Name: KEY Exam 2 ID#: November 9, 2006 Multiple choice (one point each) Circle the best answer. 1. Inducers of Xenopus lens and optic vesicle include a. pharyngeal endoderm and anterior neural plate. b. BMP4 and Fgf8. c. both a and b. 2. The most common inductive relationship is: a. epithelia inducing epithelia. b. mesenchyme inducing mesenchyme. c. epithelia inducing mesenchyme. d. mesenchyme inducing epithelia. 3. The concept of regional specificity of induction suggests that a. the source of the inducing tissue determines the structure of the induced tissue. b. the source of the induced tissue determines the structure of the induced tissue. c. the sources of the inducing and induced tissues determine the structure of the induced tissue. d. the structure of the induced tissue is independent of the source. 4. Induction that depends on cell-cell contact are called a. juxtacrine signaling. b. paracrine signaling. c. endocrine signaling. d. autocrine signaling. 5. Hedgehog, activin, and Vg1 are all a. inducing molecules. b. paracrine signals. c. receptor ligands. d. all of the above. 6. Apoptosis is mediated in many cases by a. neuroblasts. b. caspase proteases. c. endocrine factors. d. autocrine factors. 7. Resact, a sea urchin sperm chemoattractant, is produced by the a. sperm acrosomal membrane. b. vitelline envelope. c. cortical granules. 1

2 8. The sea urchin acrosome reaction and cortical granule exocytosis have in common a. Ca 2+ influx. b. K + /H + exchange. c. intracellular acidification d. all of the above. 9. Cells normally maintain an ionic condition across their membranes with a. equal Na + and K + inside. b. high Na + inside. c. high K + inside. 10. In the egg activation pathway, early responses include: a. Na + influx, fast block, Ca 2+ release, stimulation of protein synthesis b. Na + /H + exchange, fast block, increase in intracellular ph, DNA replication c. Na + influx, fast block, Ca 2+ release, slow block d. none of the above 11. Mammalian sperm capacitation involves a. membrane potential changes. b. internal ph changes. c. membrane lipid changes. d. all of the above. 12. The area of mammalian sperm that binds to the egg prior to membrane fusion is the a. membrane at tip of the head. b. inner acrosomal membrane. c. equatorial domain of the sperm membrane. 13. The point at which transcriptional control transfers from maternal to the zygotic is called the a. the mid-blastula transition. b. embryonic asynchrony. c. cleavage. d. zygotic transfer. 14. In general, cleavage patterns are determined by a. yolk content. b. yolk distribution. c. spindle orientation. d. all of the above 15. Molluscs display a. meroblastic spiral cleavage. b. holoblastic spiral cleavage. c. meroblastic radial cleavage. d. holoblastic radial cleavage. 2

3 16. At the 60 to 64-cell stage, most sea urchin blastomeres are a. committed only b. committed, but not specified c. specified and committed d. specified, but not committed 17. In early sea urchin embryogenesis, induces endodermal and mesodermal fates. a. β-catenin b. veg2 c. an1 d. aboral ectoderm 18. Which cell movements are closely associated with sea urchin gastrulation? a. epiboly, delamination b. ingression, invagination, convergent extension c. invagination, epithelialization d. all of the above 19. The Gurken protein in the posterior of the Drosophila oocyte eventually results in the orientation of microtubules such that their a. growing (+) ends are at the posterior. b. non-growing (-) ends are at the posterior. c. growing (+) ends are at the anterior. 20. On the dorsal follicles of Drosophila oocytes, Gurken binds to Torpedo and prevents a. Toll receptor binding. b. Pipe protein synthesis. c. Dorsal protein activation. d. All of the above. 21. In Drosophila, the Dorsal protein produces a. dorsal traits. b. ventral fates. c. posterior fates. 22. Choose the correct gene activation hierarchy a. maternal effect, gap, pair-rule, segment polarity, homeotic selector b. maternal effect, gap, segment polarity, pair-rule, homeotic selector c. maternal effect, pair-rule, gap, homeotic selector, segment polarity d. gap, maternal effect, pair-rule, segment polarity, homeotic selector 23. The Bicoid protein prevents caudal gene expression by a. binding to the enhancer and repressing transcription. b. binding to the 3'-untranslated region and preventing translation. c. acting as a ribonuclease and degrading the message. d. preventing transport of the message by microtubules. 3

4 24. The terminal regions of the Drosophila embryo are specified by the interaction of a. Bicoid and Nanos proteins. b. Gurken and Torpedo proteins. c. Delta and Notch proteins. d. Torso and Torso-like proteins. 25. The Drosophila pair-rule genes are expressed in embryonic a. segments. b. parasegments. c. intersegments. True / False (1 point each) 26. In the RTK pathway, the ERK factor phosphorylates a transcription factor. T 27. Spawned sea urchin eggs undergo final polar body extrusion after fertilization. F 28. The bicoid gene binds to dynein ATPases and moves to the + end of the microtubule. F 29. An instructive signal initiates new gene expression in a responding cell. T 30. Mouse sperm acrosome reactions are stimulated by fucose sulfate polymers. F 31. Sea urchin sperm will not bind to a membrane with a positive potential. T 32. Sperm contribute DNA and mitochondria to the zygote. F 33. The size of cleavage stage blastomeres is determined by the position of the spindle. T 34. The Drosophila Torpedo receptor is the homologue of vertebrate Hedgehog receptor. F 35. Drosophila segments and parasegments are one compartment out of phase. T Matching (1 point each) Make the best connection. 36. _b_ Notch a. competence factor 37. _g_ Gurken b. Delta 38. _i_ SMAD c. paracrine factor 39. _a_ Pax6 d. male pronucleus 40. _c_ Activin e. homeotic selector 41. _j_ Cyclin B f. N-acetylglucosamine 42. _f_ galactosyltransferase g. Torpedo 43. _h_ Nodal h. left-right axis 44. _e_ Ultrabithorax i. signal transduction pathway 45. _d_ protamine j. cdc2 4

5 Short Answer. (5 points each; answer any five questions.) 46. Define mesenchyme and epithelia. mesenchyme loosely packed, unconnected cells, derived from mesenchyme; surrounded by extracellular matrix epithelia sheets or tubes of connected cells; originate from any cell layer; characterized by tight junctions 47. List four mechanisms by which cells can maintain a differentiated state through regulation of gene transcription 1. transcription factor binds its own enhancer 2. synthesized protein permanently stabilizes the promoter chromatin 3. synthesize an autocrine signal 4. reciprocal interaction with neighboring cells 48. List the major events taking place during fertilization. 1. sex mixture of two genomes 2. reproduction activation of the egg and start of development 49. The receptor tyrosine kinase signal transduction pathway contains multiple activation steps. Order the following molecular components correctly, starting from the cell membrane to the nucleus: ERK, ligand binding, GNRP, MEK, RAF, RAS, RTK, transcription, transcription factor ligand binding, RTK, GNRP, RAS, RAF, ERK, transcription factor, transcription 50. List the contents of the sea urchin egg cortical granule. - serine protease (or proteolytic enzymes) - mucopolysaccharides - adhesive glycoproteins - hyaline (protein) - peroxidases 51. What are the general steps in the interactions between sperm and eggs? - sperm chemoattraction - acrosome reaction (acrosome exocytosis) - sperm binding to extracellular envelope (vitelline envelope/zona pellucida) - passage of sperm through extracellular envelope - fusion of egg and sperm membranes - pronuclear fusion 52. Explain the control of the cell cycle in 1) early cleavage stage embryos and 2) adults. Common - cyclin B bind to and activates cdc2 = active cyclin-dependent kinase (CDK; also known as mitosis-promoting factor; MPF) - MPF stimulates cell division (mitosis) - cyclin B degrades - inactivating MPF - cell goes into either S phase or G phase; growth, DNA synthesis Cleavage-stage embryo- maternally supplied cyclin B binds to cdc2; cycle repeats Adults - cyclin B must be re-synthesized, creating time for growth (G1, G2) phases 5

6 Short Essay. (10 points each; answer any three questions). Use the space provided or the back of the sheet for text and diagrams, if needed. Make sure your answers are complete and any diagrams are appropriately labeled. 53. In your research you discover a species of sea urchin that has evolved internal fertilization. What differences in the interactions between the sperm and eggs of this new species and those found in the common, externally-fertilizing sea urchins might you expect to find? - fewer sperm - less emphasis on species-specificity mechanism e.g. - surface recognition proteins (bindin/receptor) less specific - acrosome reaction-stimulating mechanism less specific - chemoattraction - reduction in efficiency of blocks to polyspermy 54. These graphs show the relative concentrations and positions of several mrnas and proteins during two stages of Drosophila development. 1. Label the appropriate lines with the following: nanos mrna Nanos bicoid mrna Bicoid hunchback mrna Hunchback caudal mrna Caudal 2. Interpret the graph. In other words, explain what each line represents and why they change between the two graphs. (A) Oocyte contains stabilized messages: bicoid mrna in the anterior nanos mrna in the posterior hunchback and caudal messages are distributed uniformly throughout the embryo (B) Early cleavage embryo messages have been transcribed and proteins are diffusing through the cytoplasm: Bicoid protein diffuses posteriorly; sets up anteriorposterior concentration gradient Nanos protein diffuses anteriorly; sets up a posterioranterior concentration gradient Hunchback is produced in the anterior, but translation in the posterior is inhibited by the Nanos protein Caudal protein is produced in the posterior, but translation in the anterior is inhibited by the Bicoid protein 6

7 55. In the Drosophila oocyte, the Dorsal protein contributes to the specification of mesoderm and neurogenic ectoderm, along with several other tissues. How can the same protein contribute to the specification of different cell fates? Describe as many mechanisms as possible that Dorsal uses to achieve multiple specification effects. - multiple genes with enhancers for Dorsal - enhancers with different affinities for Dorsal - Dorsal enhancers in combination with enhancers for other transcription factors - Dorsal inhibits dorsalizing genes 57. Describe the events taking place in the slow block to polyspermy in the sea urchin. - cortical granule reaction: - internal calcium ion release from endoplasmic reticulum - fusion of cortical granule membrane with overlying plasma membrane - release of cortical granule contents into perivitelline space - progressive release of Ca 2+ stores from endoplasmic reticulum - serine protease digestion of protein connections between plasma membrane and vitelline envelope - osmotic swelling of fertilization envelope stimulated by polysaccharides released from cortical granules - release of hyaline into perivitelline space - hardening of vitelline envelope by cortical granule peroxidases Bonus question (2 points) Where is the nucleus of the human oocyte just prior to completion of meiosis? Just under the plasma membrane; extrusion of a very small polar body means that the spindle must be located at a position where minimal cytoplasm would be incorporated. 7