One of the wonders of the universe is that we all start as the union of a sperm and and egg. Now in itself that is not at all spectacular. The the cleavage of the first nucleus leads to two cells exactly alike. And again a division and we have four cells exactly alike and so on again and again. Still nothing wondrous . But the cells in our bodies are not all the same. We have legs and brains and kidneys, et cetera. At what point do cells differentiate, or change from being 'exactly alike' to 'this is an arm', or eye or whatever? Do the cells count how many times they've divided? One suggestion I've heard is that the 'exactly alike' cells become formed into a basket like formation after five or six divisions in which although the cells are alike in terms of their DNA, they are different for spatial reasons which would cause different electrostatic charges on different cells which would make them different enough to become the specialized cells needed to build our bodes. That's the wondrous part.
N'est pas?
Cell differentiation is another indicator that we're all on this flight together.
Dick
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