Review for the third hour exam, part five Some of these may be similar to questions previously posted. Remember that you should be able to identify any figure or photograph in the lecture notes from this part of the course, or sketch such a figure. The same applies to the videos that are linked to the lecture notes. 119) Describe the formation of cartilage and bone in a developing limb. 120) Draw a cross-section of the apical ectodermal ridge of a bird. 121) What is unusual about the apical ectodermal ridges in embryonic salamander limb buds? 122) How did researchers cause developing salamander legs and chicken wings to branch into three? 123) What inductive signals could cause such triple branching? 124) When a (previously hemispherical) human embryo develops its apical ectodermal ridge, what changes in symmetry occur? 125) What are blastemas and where are they found? 126) If you cut off the leg of a salamander, what is the origin of the new muscles that replace those that were cut off? 127) What misinterpretation did Wilson make in his observations about sponge cell re-aggregation? 128) When salamanders regenerate their legs, what are two fundamentally different processes that might be responsible? Hint: they are related to Wilson's misinterpretation. 129) Make a sketch of what Liesegang rings look like. 130) What is the distinction between necrosis versus apoptosis? 131) What are at least five normal functions of programmed cell death (apoptosis)? 132) What are caspases? 133) What is the bcl-2 protein? How does it function in programmed cell death? 134) If you invented a drug that somehow activated caspase enzymes inside any cell whose mitochondria are less active than usual, and/or in which there are abnormally high concentrations of lactic acid, then what medical purpose could your drug be likely to serve? (And explain how and why). 135) Sketch the process of VDJ recombination. When does this occur? 136) Suppose that the random DNA splicing during embryonic development of a B-lymphocyte resulted in production of antibodies that exactly fit the type A blood group substance. Would that be more or less likely to occur in a person with type A blood, as compared with a person type O blood? Please explain why. What would be the end result in each case? 137) Researchers have discovered that cleavage-stage mouse embryos can merge with rat embryos at the same stage, and develop into animals in which some parts consist of mouse cells and other parts are rat cells. Why do the immune systems of these "chimeric" animals not produce an autoimmune attack on any parts of their body? 138) Suppose that you grafted mouse tissue into a rat-mouse chimera, would the graft be rejected by the chimera's immune system? Explain why or why not 139) What if you grafted tissue from such a rat-mouse chimera into an adult mouse, would that graft be rejected by the mouse's immune system. 140) What is the error in the following misleading statement? "Autoimmune diseases result from failure of lymphocytes to distinguish between 'self' and 'non-self' histocompatibility antigens." 141) Describe a possible cure for multiple sclerosis (which can be the one proposed in the lecture notes, or a different one that you either invented yourself, or that you got from some other source). 142) What causes blockage of arteries in atherosclerosis? 143) When and for what purposes do the plasma membranes of oocytes become much more permeable to sodium and calcium ions? 144) What is electroosmosis? In what processes is it important? 145) What are cortical vesicles?