Fertilization yes or no circle your response why e 55

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FERTILIZATION? YES or NO (Circle your response) WHY?
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E-55, Exam 1-2010: Name Page 7 of 8 25. (12 points, 3 points each for A-B, 2 points each for C-E) A new species of fish is discovered living in Lake Michigan, and they are termed ‘michifish’. Michifish eggs are large, almost as big as a frog egg, and are amenable to the physical manipulations that we have discussed. Interestingly, michifish eggs have a lovely purple color. Upon fertilization, the purple pigment in the michifish embryo becomes concentrated to the vegetal pole. At late stages of embryogenesis the liver alone retains the purple color. To test if the purple substance confers liver fate, you prick a tiny hole in a fertilized michifish embryo using a needle and remove the purple cytoplasm. You see that the hole seals itself, and then development proceeds normally but with one major hitch: the resulting embryo fails to make a liver. A. In 1-2 sentences, what does this suggest about the mechanism of liver development in the michifish? B. In 1-2 sentences, what does this suggest about the overall mechanism of development for the michifish? C. What 1-word term would best describe the purple substance? ___________________________ D. Without any additional knowledge about the identity of the purple substance, how could you test if the purple substance is sufficient for liver formation ? In your answer, make a reasonable speculation about the phenotype you might expect to see in your experiment if the purple substance is sufficient for liver formation. E. What type of molecule could the purple substance be? List two possible types of molecules based on your understanding of the categories of materials that are present in an egg. 1. ____________________________________ 2. ____________________________________
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E-55, Exam 1-2010: Name Page 8 of 8 26. (12 points, 2 points each for A-C, 6 points for D) You are a graduate student in Stu Orkin’s lab at Childrens Hospital Boston, a lab that has an international reputation for studying transcription factor control of blood development. You find a novel transcription factor that is highly expressed in the blood and are very excited at the prospect of contributing to the long-standing lab legacy with your research. You rush to make a mouse knockout without any further experiments, and find that your homozygote knock-out mice die during early gestation. A. What is the most likely explanation for this result? You realize that you should you have employed some other techniques to find out more about the expression of the transcription factor during embryogenesis. B. Name two techniques that would have told you information about expression of the gene. 1. ____________________________________ 2. ____________________________________ C. Given the embryonic lethality of the knockout, what technique will you now use to knockou t the transcription factor just in the developing blood ? (Hint: You have numerous blood-specific promoters at your disposal in the Orkin lab.) ______________________________________________ D. How does this technique interfere only with blood development? Clearly describe AND ALSO draw simple diagrams to illustrate the DNA constructs that you will use to engineer the system you listed in part C.
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