Exam 1 ID#: June 23, Multiple choice (one point each; indicate the best answer)

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1 Biology 4361 Name: KEY Exam 1 ID#: June 23, 2008 Multiple choice (one point each; indicate the best answer) 1. Which of the following agrees with von Baer s laws: a. The embryos of mammalian species resemble adult stages of amphibian species. b. General features appear earlier in development than do specialized features. c. both agree d. both disagree 2. The epigenetic theory of development a. required the growth of new structures during development. b. explained the mixture of traits in hybrids. c. was hampered by the perceived need for a vital force. d. all of the above. 3. Diploblastic animals lack a. true mesoderm b. true endoderm c. true ectoderm d. germinal epithelium 4. A fate map a. determines whether a particular blastomere will survive. b. predicts the point at which a cell will move to a new location. c. tracks the differentiation pathway for a cell or group of cells. d. tracks the movement of stem cells through differentiation. 5. Cleavage can be described as a. increase in cell number, but no cell growth. b. cell growth, but no increase in cell number. c. nuclear division without cytoplasmic division. d. cytoplasmic division without nuclear division. 6. Transplantation of tissue from one embryo to another of a different species is called: a. heterospecific b. heterochronic c. homospecific d. homochronic 7. Crossing over occurs during which stage of meiosis a. prophase I. b. prophase II. c. anaphase I. d. none of the above 1

2 8. Eggs (oocytes) generally a. are produced when organisms reach maturity. b. function only as carriers of the female genome. c. provide non-genetic information necessary for early development. d. are produced in numbers equal to sperm. 9. The function of gastrulation is a. to form multiple cell layers. b. to place cells in proper orientation for future development.. c. neither of the above. d. both a and b. 10. When a Dictyostelium pseudoplasmodium is cut in half some of the posterior cells, which were fated to become spores, now become pre-stalk cells. This demonstrates a. determinative development. b. autonomous development. c. mosaic development. d. regulative development. 11. Dictyostelium myxamoebae receive chemical signals from the outside environment which are relayed intracellularly across the cell membrane. This is an example of a. evolvability b. signal transduction c. chemotaxis d. chemosignaling 12. Vertebrates undergo a. syncitial specification. b. conditional specification. c. autonomous specification. d. a blend of conditional and autonomous specification. 13. In organisms with autonomous specification the distribution of determines cell fate. a. egg cytoplasm b. maternal RNA c. egg proteins d. all of the above 14. You discover a Drosophila embryo with no apparent head, but with tails at both ends. A plausible explanation is a mutation that inactivated the gene. a. nanos b. bicoid c. Pax6 d. distal-less 15. Cell-cell adhesion is often mediated by a. carbohydrates b. cadherins c. catenins d. all of the above 2

3 16. RNA interference pathways probably evolved in response to a. hybridization. b. cross fertilization. c. double stranded RNA viruses. d. double stranded DNA viruses. 17. RNA interference involves which enzyme complex a. dicer b. phosphodiesterase c. endonuclease d. exonuclease 18. Histone de-acetylation gene transcription. a. allows b. increases c. inhibits d. has no effect on 19. You remove a set of cells from an early embryo and observe that the adult organism lacks the structure that would have been produced from those cells. You conclude that the species undergoes a. autonomous specification. b. syncitial specification. c. conditional specification. d. none of the above. 20. Morpholino-antisense oligomers differ from normal antisense RNA in that they a. degrade quickly, so that transient effects can be studied. b. do not degrade quickly, so that long-term effects can be studied. c. can be visualized using fluorescent microscopy. d. are unable to enter the nucleus. 21. To be considered a morphogen gradient, a substance must have a. a source and a sink. b. the ability to diffuse through the embryo. c. a stimulatory activity on cell growth. d. all of the above 22. If a set of tissues is transplanted to an area of unlike fate, but retains its original fate, the original tissue was considered a. specified and determined b. specified but not determined c. determined but not specified d. determined but not committed 23. A characteristic of stem cells is that they each a. make multiple types of differentiated cells. b. make all types of differentiated cells. c. regenerate copies of themselves. d. die after undergoing mitosis. 3

4 24. During hnrna processing, which of the following modifications is made? a. A methylated guanine is added to the 3 end. b. A methylated guanine is added to the 5 end. c. A methylated guanine is added to the 3 end in reverse orientation. d. A methylated guanine is added to the 5 end in reverse orientation. True / False (1 point each) 25. The first observable cellular activity in the oocyte after fertilization is cytoplasmic rearrangement. True / False 26. Histone methylation represses transcription. True / False 27. Muscles and bones are generally derived from mesoderm. True / False 28. Dictyostelium demonstrate a modified form of syncitial specification. True / False 29. In Drosophila the syncytial blastoderm stage is followed by the cellular blastoderm stage. True / False 30. The light bands seen in polytene chromosomes are heterochromatin. True / False 31. More than one system of specification can be observed in some species. True / False 32. Retroviral vectors are commonly used to create pores in the cell membrane. True / False 33. Gene messages can be detected using in situ hybridization. True / False 34. RT-PCR is used to compare the production of specific proteins in different tissues. True / False 35. The DNA in chromatin consists of repeated sets of about 140 base pairs wrapped around a histone core connected together by a 60 base pair linker (Greg s question). True / False 36. Adding a methyl group to histones generally increases gene activity. True / False 4

5 Fill in. (1 point per answer) Use the terms from the Term Bank to make the most accurate sentence. Term Bank antibiotic resistance blast committed stem cells dermal Dicer fate histone acetyltransferase histone deacetylase hormones knockdown knockout methylase mosaic phosphodiesterase morphogen pluripotent stem cells potency RISC syncytium TATA box transfection transposable elements 37. The term blast refers to cells or tissues that make up formative units of living matter. 38. A cell undergoing nuclear division without cell division is referred to as a syncytium. 39. The enzyme histone acetyltransferase is associated with transcriptional activation. 40. As a blastomere develops, its potency generally decreases as it progresses toward its fate. 41. RNAi techniques make use of the cellular enzyme Dicer, which is part of the RISC complex. 42. Foreign genes can be inserted into cells using transfection or transposable elements. 42. Intrauterine factors such as hormones can act to influence development. 43. Committed stem cells can produce committed stem cells but not pluripotent stem cells. 44. An experiment in which a gene is eliminated from an organism is referred to as a knockout, while one in which gene activity is transiently inhibited is called a knockdown. 5

6 Short Answer. (5 points each; answer any six. Be certain to address all parts of the questions.) 45. Why are different puffing patterns observed in polytene chromosomes at different times during development? - dark bands are areas of heterochromatin = transcriptionally inactive - light bands are areas of euchromatin = transcriptionally active - puffing indicates large amounts of transcriptional activity - changing puffing patterns indicates that different areas of the genome are becoming active 46.Your experiment to produce transgenic mice resulted in 25% that showed no trace of the transgene trait, 50% that showed partial expression of the trait, and 25% that died before birth. What conclusions can you draw from this data? - the transgene was incorporated into the primordial germ cells (gamete precursor cells) since the offspring were affected - however, the transgene was lethal in the homozygous condition - your results show a Punnett square distribution with 25% wild type (no effect), 50% heterozygotes (partial effects), and 25% homozygous for the transgene (lethal) 47. When you remove a blastomere from the embryo you are studying, the remaining portion of the embryo develops normally, and a complete (although smaller) organism develops from the single blastomere. What can you say about: A) the type of specification exhibited by this organism. - conditional specification; the remaining blastomeres were able to compensate for the missing cell and produce a complete embryo B) the potency of the blastomere at the time of removal. - the blastomere was either totipotent or pluripotent; the single blastomere was able to produce an entire embryo; if it was from a placental mammal, it may have been a pluripotent inner cell mass blastomere 48. In an experiment using a model species that undergoes conditional specification you transplant cells that would normally form the tip of the wing to an area that would normally form the middle joint of a leg. How would you expect to characterize the resulting transplanted cells if A) the cells were not specified - transplanted cells would be indistinguishable from the host cells (i.e. midjoint) B) the cells were specified, but not totally committed. - transplanted cells would be wing-type cells that took the character of mid-wing, instead of tip 6

7 49. Arrange the following gene features in their proper order: exons and introns, leader sequence, polya addition site, promoter region, TATA box, transcription initiation site, transcription termination site, translation initiation site, translation termination site, upstream promoter region - upstream promoter region, promoter region, TATA box, transcription initiation site, leader sequence, translation initiation site, exons and introns, translation termination site, polya addition site, transcription termination site 50. Explain the significance of the partial success of experiments using serial transplantation of blastomeres to support amphibian cloning. Earlier attempts to support development using differentiated cells was unsuccessful, but nuclei apparently gained the ability to support early development as they underwent successive rounds of transplantation, they must have been reverting to an earlier, lesser-differentiated form. These experiments established that differentiation of somatic cells was not absolutely irreversible. 51. Although Dictyostelium is a very simple organism, its developmental life cycle has parallels to systems in more complex animals. Describe how one phase or behavior shown during the Dictyostelium life cycle is similar to a behavior found in the development of a higher organism. aggregation intracellular signaling pseudoplasmodium formation cell contact/motion gastrulation stalk and spore formation differentiation, morphogenesis, organ formation spore formation - gametogenesis 52. In your experiment with sea urchin blastula you remove calcium from the medium and all of the blastomeres dissociate and can be seen as individual cells. Describe one possible explanation for this phenomenon. The adhesive properties of the extracellular matrix molecules that hold the blastomeres together may be regulated by calcium; once it is removed, the cells dissociate. 7

8 53. A) Define heterochronic transplantation. B) Describe an experimental situation or hypothesis that could be tested using heterochronic transplantation. A) Transplantation of cells or tissues from one stage of development to a host in another stage of development. B) Is the donor tissue specified or determined? Transplant it into an older (specified) portion of the embryo and test for changes in fate. Short Essay. (10 points each; answer number 51 and either 52 or 53. Be certain to address all parts of the questions.) 54. You are studying the effects of chemical X on Dictyostelium. You suspect that chemical X prevents Dictyostelium myxamoebae from specifying as spore cells if used during the migrating pseudoplasmodium stage, but that it doesn t have any effect once the culmination stage begins. Please design an experiment to test this hypothesis. You can assume that everything you need is available; mature Dictyostelium cultures, plates with E. coli lawns, microscopes, etc. are all provided. In addition, you have a solution of chemical X in water. Address the following points in your experimental design: A) State a hypothesis for your experiment. B) Describe briefly the experimental technique you would use to test the hypothesis. C) Describe the necessary control experiments that you would conduct. D) Briefly describe the expected outcome, and explain their relevance (i.e. explain what a successful experiment would prove) 8

9 55. Explain how you might perform transplantation experiments to analyze the stage of committment of developing tissues, using the concepts and terms of specification and determination. Describe hypothetical experiments and results to illustrate your answer. - transplanted to neutral areas (or culture dishes) shows whether cells are specified - if they change course or do not progress; they are not specified - if they continue to develop according to their presumed fate, they are specified - transplanted to areas that will develop different fates - if they develop into the new (i.e. host area) fates, they were not committed - if they continue to develop following their original presumed fate, they were committed 56. A) Describe in detail the method for producing a gene knockout organism. B) What is one possible reason (or use) for gene knockout organisms? - purpose - to create a line of animals that contain a transgene - method: - create embryonic stem cells containing 1) a transgene (to replace the target gene) 2) a gene for antibiotic resistance - 1 & 2 can be combined by inserting the antibiotic resistance gene within the target gene - grow the ES cells in a culture containing an antibiotic (this will kill any cells not containing the gene for antibiotic resistance; i.e. not containing the transgene) - insert the surviving ES cells, which contain the transgene and antibiotic resistance gene into the inner cell mass of a host embryo - implant the gene into the host uterus - resulting mice will be chimeric (containing cells derived from both the host and the transgenic embryo - cross the transgene chimeras with a wild-type - the f1 cross will result in transgene homozygotes = knockouts 9