April 27, 2018 How to study for the final exam in Vertebrate Embryology 2018 Review the three hour exams, especially any questions that you got marked wrong, or only got part credit. Make sure you understand how your answer should have been different in order to get full credit. I am going to ask a few of those questions again on the final exam, and to grade them more strictly. ------ Carefully study the diagram which compares early development in sea urchins, mammals, birds, & teleost fish. The final exam will contain a few parts of this diagram, and ask you what kind of animal's embryo it depicts, at what stage of development, what organs develop from cells at locations marked with an arrow. For example, the gastrulating sea urchin picture might be marked with an arrow pointing toward the cells that form the skeleton, and the question asked: "The cells at this location develop into what differentiated cell type?" The contents of this diagram are very important; Every square centimeter of it should make sense to you, and awaken memories of many concepts, principles, facts, names of structures, fates of cells, and geometries of cell rearrangements. As examples, could you find examples of invaginating epithelia? Examples of extraembryonic membranes? Major differences in gastrulation of birds as compared with frogs? Similarities in gastrulation in human embryos and birds? Structures found only in fish embryos, and not in embryos of any other vertebrates? Differences in the non-living protective shells around embryos of different kinds of vertebrate embryos? ------ Review all the photographs, drawings and diagrams that are on any of the web pages for this course. Any of them might be on the final exam. ------ You should know the origins of organs and/or differentiated cell types from ectoderm, mesoderm or endoderm, and which subdivisions of each germ layer. See final_review_part_1.htmfor a list For example: Schwann cells develop from neural crest ectoderm. Liver develops from endoderm. Skeletal muscles develop from the myotome subdivision of somite mesoderm. Gonads develop from a combination of lateral plate mesoderm and primordial cells. Teeth develop from an outer layer of enamel (stomodeal ectoderm) and an inner core of dentine (neural crest ectoderm). ------ Make sure you learn all questions from lists of questions on this past semester's web pages posted for this course. ------ Please make sure you understand the similarities of the fast block to polyspermy as compared with action potentials of nerve fibers. Also understand the similarity of the slow block to polyspermy versus what happens at synapses (voltage depolarization causing increased calcium concentrations, stimulating release of cytoplasmic vesicles full of important chemicals. ------ Make sure you understand the physical cause of swelling of cartilage. How does electro-osmosis work? What substitutes for the role played by semi-permeable membranes in regular osmosis? Is osmotic pressure a scalar or a tensor? Why? Why is this important? Is tension or pressure in a collagen gel a scalar or a tensor? Why is that important? ------ Make sure you remember the origin of DNA base sequences that code for antibody binding sites. (Hint: It is not by a stimulus from antigens.) ------ Neotenic sea urchins don't exist, but what would they be like if there were such a thing. What would neotenic butterflies be like? Over-production of which hormone might conceivably result in such a thing? ------ Dolly the sheep, in contrast, was not a surprise to embryologists. Already, for decades, since 1952, researchers had been producing animals by nuclear transplantation. (Briggs and King, 1952), Gurdon in the 1970s. All the cells have all the genes. A few exceptions are the surprises. " Imprinting " abnormal development occurs if two male pronuclei, or two female pronuclei are transplanted into the same oocyte. If Dolly and other animals produced by nuclear transplantation into oocytes turn out not to age sooner that animals born the normal way, what implications would that have for the idea that aging results from shortening of telomeres? What about theories that aging results from accumulations of somatic mutations? What about getting the nuclei from cells that have been living in tissue culture for various lengths of time? What ought to happen? Hint: Maybe being put into an oocyte causes telomeres to increase greatly in length?

 

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