SQ1 - MCDB 112, F10 Study Questions, Set #1 Covers...

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Unformatted text preview: MCDB 112, F10 Study Questions, Set #1 Covers (roughly) Lectures 1-3 Study Questions are meant to help you review material presented in lecture in preparation for the exams. Ideally, the SQs help you develop an applied understanding of the material. We recommend writing out the answers to the SQs as if they were exam questions. Many students read the questions, formulate a mental answer, but then struggle with exams because they do not “practice” how to put the answer – correct or not -- down on paper. For most students, actually writing out the answers – and checking to make sure they are “full credit answers” is very helpful. You can have Dr. Foltz or the TA review your answers (email or hard copy). Questions or further details about the SQs are also appropriate for Discussion section review. Similarly, taking last year’s exams as “practice” is very useful - -as is going over questions in depth during discussion. 1. What is meant by the phrase “the genome in the early embryo is silent?” If the embryonic (zygotic) genome is “silent,” then how is it that the embryo is undergoing cell division and developing? 2. What do we mean when we call an animal “triploblastic?” 3. Suppose that you observe that a protein called “FFT” is always present in cells that take on the fate of “lymph tissue” during development. You are unable to detect FFT mRNA or protein in other cell types. Suggest a hypothesis about the role of FFT in specifying lymph cell fate, based on this correlative evidence (write out your hypothesis in the form of a sentence). Now propose experiments that test your hypothesis. One experiment should be a LOF (necessity) test and the other a GOF (sufficiency) test. For each experiment, clearly state the predicted outcome if indeed your hypothesis is correct. Do not worry too much about exactly how you would go about doing the experiment (technical aspects) but rather focus on the basic approach that you would need to use. In Discussion section (or office hours), you can talk about the possible technical aspects and especially control experiments and interpreting experimental results. 4. Over time, blastomeres acquire specific fates. There are two steps of cell fate acquisition, regardless of the mechanism directing the cell fate. What are those two steps and how could you distinguish between experimentally? 5. Describe the two basic mechanisms by which cell fates are acquired. Be clear about the differences. From an experimental (embryo manipulation) point of view, how would you distinguish between these two basic types of cell fate acquisition mechanisms? 6. Suppose that you conduct blastomere isolation experiments on an embryo in an effort to begin to determine its fate acquisition mechanisms. Here is the fate map (or lineage trace) of the blastomeres of an embryo at the 4 cell stage: epidermis epidermis gut and nervous system mesoderm derivatives Here is what happens when you isolate and culture blastomeres at the 4 cell stage (each blastomere divides in culture, but does not form an embryo): epidermis gut epidermis mesoderm derivatives 6A. Based on this, what can you say about the mechanism of cell fate acquisitions, at least at the 4 cell stage? 6B. Specifically, what is your conclusion about how the nervous system cell fates are acquired? Explain. 6C. State a hypothesis about how nervous system cell fates are acquired and then design an experiment that tests your hypothesis. Include controls and predicted outcomes with explanations. 6D. When you look at the cells in the culture dishes from the isolation experiment, how do you “know” what fate they have taken on? That is, how do you determine if they are epidermis, muscle, gut, etc…(note that they do not have a distinctive morphology that allows you to simply visualize and ID them under the microscope). 6E. Finally, you do another experiment, this time isolating the blastomeres at the 2 cell stage. In this case, two normal embryos form, one from each blastomere. What does this result tell you about the acquisition of cell fate information in relation to your answer to #6A? Explain. 7. Cells in an epithelial sheet may transition to mesenchyme. How can this be explained in terms of cell surface molecules (theory of differential adhesion)? ...
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