4 ms·

I think I get what you're trying to say. But it does not really explain certain phases of this process, in the beginning, where cells are dividing exponentiall

by udev 6y ago

I think I get what you're trying to say. But it does not really explain certain phases of this process, in the beginning, where cells are dividing exponentially and suddenly a fold appears, and simultaneously many cells, many being far apart, start behaving differently from other cells just next to them. So whatever chemistry or physics foundation helps achieve that, it has this capacity to be very selective (these cells far apart do it, but these ones next to them don't), i.e. it is not temperature, acidity/base concentration, pressure, or other basic physics, because these phenomena don't have this kind of selectivity.

shmageggy 6y ago
I think such basic phenomena have more power than it would seem. I’m not a biologist, but from poking at wikipedia: > Turing correctly predicted a mechanism of morphogenesis, the diffusion of two different chemical signals, one activating and one deactivating growth, to set up patterns of development https://en.wikipedia.org/wiki/Morphogenesis https://en.wikipedia.org/wiki/Morphogenesis > cells move to be near other cells of similar adhesive strength in order to maximize the bonding strength between cells and produce a more thermodynamically stable structure https://en.wikipedia.org/wiki/Differential_adhesion_hypothesis https://en.wikipedia.org/wiki/Differential_adhesion_hypothes...
kaba0 6y ago
Though it is sort of well understood in embryology. It was quite some times ago I studied it, but the big picture is that each cell starts out as a so-called pluripotent cell, that can turn to every other cell type. The important first step is axes selection (head-tail, left-right). The left-right axes is selected in a really interesting way, cells in the middle have a little flagella that tends to rotate in a specific direction. (If my memory is right, the condition where someones internals are all mirror images of “normal” is caused by some problem with these) Now secreted signal molecules will be concentrated on one side, and this selects the given side. But the big picture is that each cell has a decision tree, and local signal molecule concentration is the criteria on which they decide. And later each cell has the ability to express yet another signal molecule and so on. If we were to imagine a 2d plane and you could symmetrically place a secretion center of A and B signal in a left and right region respectively, than you can have a new type of cell in the middle if it changes based on “signal A and B is on”.

by udev 6y ago

shmageggy 6y ago

I think such basic phenomena have more power than it would seem. I’m not a biologist, but from poking at wikipedia: > Turing correctly predicted a mechanism of morphogenesis, the diffusion of two different chemical signals, one activating and one deactivating growth, to set up patterns of development https://en.wikipedia.org/wiki/Morphogenesis https://en.wikipedia.org/wiki/Morphogenesis > cells move to be near other cells of similar adhesive strength in order to maximize the bonding strength between cells and produce a more thermodynamically stable structure https://en.wikipedia.org/wiki/Differential_adhesion_hypothesis https://en.wikipedia.org/wiki/Differential_adhesion_hypothes...

kaba0 6y ago

Though it is sort of well understood in embryology. It was quite some times ago I studied it, but the big picture is that each cell starts out as a so-called pluripotent cell, that can turn to every other cell type. The important first step is axes selection (head-tail, left-right). The left-right axes is selected in a really interesting way, cells in the middle have a little flagella that tends to rotate in a specific direction. (If my memory is right, the condition where someones internals are all mirror images of “normal” is caused by some problem with these) Now secreted signal molecules will be concentrated on one side, and this selects the given side. But the big picture is that each cell has a decision tree, and local signal molecule concentration is the criteria on which they decide. And later each cell has the ability to express yet another signal molecule and so on. If we were to imagine a 2d plane and you could symmetrically place a secretion center of A and B signal in a left and right region respectively, than you can have a new type of cell in the middle if it changes based on “signal A and B is on”.