Discussion: There are three journal articles that will be made available to you after you complete the Western blot. These are primary research articles that describe studies on the signal transduction of sea urchin fertilization. Read the abstracts for each of these articles first to see what information they contain. You will need to carefully read through at least two of them to get the information you will need to write the discussion section for your report. In general, take some time and really put some thought into your discussion section. Your score on this part of the report will be based on how well you make your arguments.
Begin your discussion section by going into an in-depth analysis of your data and interpreting it to answer your two questions about the calcium influx. Answer both questions and carefully go through your reasoning. Refer to individual lanes on your films when answering the question on MAP kinase.
If the bands in some lanes are not consistent with the overall pattern, discuss if this might be explained by the egg activation data (if the treatment didn’t activate the eggs, it won’t have the expected downstream effect either).
The way you performed your experiment asked the question, “Is Ca2+ sufficient for induction of cell division and inactivation of MAP kinase?” so frame your discussion with this in mind. After you have answered whether Ca2+ is sufficient for MAP kinase inactivation from your data, discuss whether your conclusion is consistent with the results described in the journal articles. Do these articles reach the same conclusion about the Ca2+ influx and MAP kinase? You must provide one reference for this from these articles.
Next, since your experiment asked if Ca2+ was sufficient for MAP kinase inactivation, propose a different experiment that could be done to ask if Ca2+ is necessary for MAP kinase inactivation. Use the articles to help you find a technique that would allow you to do this, and provide the reference (different from your first reference) from those papers or an outside source. Give a brief descriiption of the reagents that you would use for this experiment. You should also explain what result you would expect if Ca2+ is necessary for MAPK inactivation, and what result you would expect if Ca2+ is not necessary for MAPK inactivation.
Finally, take all the information you have gained about MAP kinase and go a step further to discuss the role of MAP kinase in the entry of the zygote into the cell cycle at fertilization. Unfertilized eggs are arrested in G1, and then enter S-phase after fertilization. After the cell has replicated its DNA, it enters M-phase (mitosis) and divides. Based on what you know, is inactivation of MAP kinase at fertilization necessary, sufficient, or both, to get the egg to enter the S-phase of the cell cycle? Also, is the inactivation of
MAP kinase at fertilization necessary, sufficient, or both, to get the zygote to undergo cleavage? Use the information gained from your experiments and the articles on Canvas to discuss the answers to these questions. You should describe the experiments from the journal articles and the information they provide. You must cite a third article (different from the first two) to support your conclusions here.
