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ex1_2009_key - Name Student ID Zoo 470 Exam 1 Spring 2009...

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Name: _____________________________ Student ID:_________________ Page 1 Zoo 470 - Exam 1 - Spring 2009 – February 25, 2009 This exam has a total of 6 pages and a total of 50 points . You will have 90 minutes to complete it. Please put your name and student ID on all pages. Good luck! 1. Provide brief definitions for each of the following ( 6 points ): a. spermatid: Haploid product of male meiosis that, upon further differentiation, becomes a mature sperm cell.. b. Smad: Proteins activated by the TGF-b/BMP pathway. Smads transduce TGF-b signals to the nucleus by forming a complex that enters the nucleus to alter transcription. c. compaction: Cadherin-dependent increase in adhesion of mammalian embryos at the 8-cell stage. d. transdifferentiation: Process by which a differentiated cell can be converted to another differentiated cell. Recent work by the Melton lab showed this is possible in the mammalian pancreas. e. fate mapping: Process by which cells in an early embryo are followed to see what progeny they make later in development. Fate mapping can involve applying bits of color to the exterior of the embryo, simply watching embryos carefully, or injection of a tracer into the cytoplasm of individual cells. f.: broadcast spawning: Process of gamete release often exhibited by aquatic species, in which large numbers of gametes are released, and gametes rely on chance encounters for successful fertilization. Sea urchins are an example. 2. MPF and cytostatic factor are known to regulate meiotic cell divisions. Answer the following questions, based on your knowledge of these factors' effects on cell division. a. If purified CSF were injected into one cell of a two-cell embryo immediately after first cleavage, what would you predict would happen at the time of the next division? Clearly state your reasoning. ( 2 points ) At the next division, the injected cell would arrest at metaphase, since CSF would stabilize MPF, preventing its breakdown.
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Name: _____________________________ Student ID:_________________ Page 2 2 (cont) b. Recall that frog eggs can be artificially activated by pricking them with a needle, initiating the same physiological changes as fertilization. What would you expect would happen to levels of MPF within a few minutes after pricking an egg? Clearly state your reasoning . ( 2 points ) Calcium elevation leads to CSF breakdown in such an oocyte, quickly leading to MPF inactivation (i.e., decrease in MPF activity) 3. You have isolated a gene that you believe encodes a novel sperm cell surface protein, headline , and you are making a presentation to a major pharmaceutical corporation for research support to work on this protein. a. You come to the presentation armed with the following pieces of data. For each of the following facts, state the technique(s) you used to obtain your data. If more than one technique is required, list all techniques necessary. ( 4 points ) Discovery Technique(s) Used for Discovery When viewed under the microscope, human sperm extracted from the epidydimis lack headline mRNA immunostaining The mouse headline genomic DNA region has a size of 2.6 kB Southern blot Excess headline protein in male zebrafish
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