More Questions For Class Discussion: Nov 10, 201734) What does it suggest about the cause of aging that Dolly the sheep died at an unusually young age for a sheep? In fact, she died of a common cancer, and had arthritis.
35) Invent further experiments to test your hypothesis, and other hypotheses. For example, what if you compared lifespans of animals developed from grafting nuclei into oocytes taken from females of different ages? What if you compared life spans of sheep derived by implanting oocytes into young females versus older females? What about comparing results of grafting oocytes from young sheep, as compared with the result when the oocytes were grafted from older sheep? What about deriving the nucleus from tissue cultured cells that had been in culture for ten years, as compared with the result of getting nuclei from cells that had only been in culture one year? What if you got nuclei from young sheep, from older sheep, from very old sheep?
36) Many people believe that cancer cells grow faster, and divide more rapidly than normal cells. Do you know any evidence that this is true?
37) Please design an experiment to test whether cancer cells grow faster? Invent several more possible tests?
38) If a normal cell had a mutation that speeded up its rate of growth, would that cause the cell to be cancerous?
39) Could you diagnose cancers by injecting animals with radioactively labeled tritium and comparing the amounts of radioactivity incorporated into the animal's cells? Or would the more useful variable be the percentage of nuclei that have become radioactive?
40) What if a cancerous cell had a mutation that slowed down its growth rate, would that cause it not to be cancerous any more?
41) Suppose that you fused a cancerous liver cell with a cancerous skin cell, why might you expect that the resulting heterokaryons would not have cancerous properties?
42) Could you learn anything important from comparing the ratios of nuclear volume as a percentage of volume of entire cells?
43) Would you expect that cancer cells would tend to be abnormal in this ratio of volumes (nuclear volume as a % of entire cell volume)? Would you expect cancer cells to be bigger or smaller relative to the sizes of their nuclei?
44) How might such facts be used to help develop better cures?
45) In fact, faster growing cells, whether cancerous or not, are more sensitive to being killed by drugs that block DNA synthesis, or that block mitosis. Would you have expected this fact? Does it seem "logical" to you? Can you explain your reasoning process, that led you to that expectation?
46) Haploid frog cells have half the volume of diploid cells of the same species. Tetraploid cells have double the volume of diploid cells. Suggest control mechanisms that would produce this result.
47) Would you expect haploid embryos to be smaller, larger, or the same sizes as diploid embryos? What could the answer to that question help to tell you about control mechanisms?
48) If you carefully recorded the times when early embryonic cells divided, and compared haploid embryos to diploid and tetraploid embryos, what would you expect? Would haploid cells divide more, or less, rapidly? Or with shorter intervals between mitoses? Or would haploid cells continue to divide for a longer total time as in diploid embryos, or as in tetraploid embryos?
49) What are the most relevant variables? How long it takes to copy more DNA? The means by which cell volumes are made smaller in haploid cells?
50) Some species of salamanders have 25 times as much DNA per cell as human cells, and their cells are 25 times bigger than human cells? What are some possible explanations? How could they be tested?
51) Do you suppose that these salamanders have more genes? That they have 25 times as many copies of the same genes? That they have more introns, or bigger introns? Or bigger telomeres? Or more "junk" DNA? Or something else?
52) When Driesch separated the first two cells of an embryonic starfish, what surprised him so much that he concluded the causal mechanism must be super-natural?
53) If Driesch had killed one of the first two cells, rather than separating it, what would the result have probably been?
54) What does it tell us about normal mechanisms of development that very different results are produced by separating early embryonic cells, as contrasted with the result of killing one of the first cells? For example, can dead cells continue to participate in communication of signaling and detecting locations of embryonic cells.
55) Capillaries are surprisingly dynamic, and apparently can detect blood flow. At every location where net flow becomes small, capillaries constrict and their component endothelial cells actively crawl to new locations. Please invent possible mechanisms by which blood vessel cells could distinguish how much blood is flowing at different locations.
56) At high altitudes, humans and other animals respond by increasing numbers of red blood cells per volume ("hematocrit" %), and also develop more capillaries per volume of tissue.. Please suggest possible mechanisms by which decreased oxygen could cause a proportionally increased number of capillaries per volume.
57) Two of the many abnormalities of cancer cells are (i) secretion of large amounts of lactic acid, and (ii) reduced use of the Krebs cycle to convert ADP to ATP (instead using glycolysis). "The Warburg Effect" was discovered in 1924. On what basis could you determine to what degree these abnormalities are causes, results or side effects of cancer. Suggest how these phenomena are related to each other, which is cause and which is effect, how they can be used to map cancer in the body, and whether these abnormalities could improve the specificity of chemotherapy treatments. A big difficulty is that cancer cells are also abnormally insensitive to acidity and low oxygen.
58) If a structure's surface contracts with equal force in all directions, that is sufficient to re-shape the structure into a sphere. If forces vary with direction, other shapes will be produced. Does this mean that the eye-ball is shaped by the amounts and directions of physical tensions in its outer layers. Would the eye-ball and the cornea be able to keep their shapes if the tensions of their surfaces varied from place to place, or in some direction relative to others.
59) If you measure the elastic tensions in the surfaces of cylindrical balloons and pipes, it turns out that tension in the circumferential direction is always exactly twice as strong as tension in the longitudinal direction. Assuming that is true, would it mean that any material, including masses of cells, at the surface of which physical tensions become (for any reason) twice as strong in one direction as compared with the direction perpendicular to that.
60) Many anatomical structures are cylindrical: the notochord, the spinal cord, blood vessels, ducts, intestinal villi and crypts, and hairs. How can genes cause populations of cells to rearrange spontaneously into cylinders.
59) Are complicated equations the only way to generate complex patterns?
60) Why not?
61) If the surfaces of two masses of cells obey the same equations, will they develop the same shape?
62) Can changes in physical properties cause changes in geometric shapes?
63) Can you think of examples in which human engineers cause materials to rearrange spontaneously into a particular shape?
64) Can you think of (or invent yourself) any such examples of self-creating shapes in which the shape is something other than a sphere?
65) Did you know that really super-big curved mirrors for reflecting telescopes are now made by rotating sheets of glass so that the counter-balance of gravity and centrifugal force produces the perfect "sine of revolution". This is an improvement on grinding: cheaper, more accurate, and produces lighter lenses.
66) Can you visualize a computer program into which you can input a surface shape, and the output of the program will be a minimum set of properties that a material would need to have in order to re-shape itself to create that surface shape.
67) Can two different sets of properties cause materials to create the same shape?
68) Why do scientists systematically avoid studying phenomena in which tiny differences in initial conditions tend to magnify themselves into big differences in results? "Lack of reproducibility".
69) Why does the position of the moon affect the tides about 4 times more than the position of the sun. It is NOT because the moon's gravity is stronger, because it isn't.
The sun pulls harder on the earth than the moon does; but the pull of the moon changes more rapidly as a function of distance. because its closer.
70) Don't let the following claims impress you; but please give them some thought.
Integrals of forces are energies; So derivatives of energies are forces; which is why minima of energies are stable counter-balances of opposing forces.