Cell cycle

The proliferon model illustrates some important features of embryogenesis. We start with the cell cycle. Before a cell  enters mitosis and divides, it traverses three preparatory phases: G-1, S, and G-2. During the first it prepares enzymes for DNA multiplication. S, stands for synthesis.  During this phase the cell doubles its genetic material. During the G-2 phase it prepares for cell division (mitosis).

The image below depicts  embryogenesis of a simple worm. During each division the stem process creates a transient process whose structure differs from division to division. Before each division CA-1 sets CA-2 max age to a different value, which accounts for the different structures.

The next image depicts worm structure at the last state of each CA-2.  The worm consists of CA-1+CA-2. Following each division the worm acquired new functions, which are inherent in its structure. The functions specified on the right are provided for  illustrative purposes.

We may now distinguish between two kinds of differentiation: Global and local. The first marks the change of the stem process. Although its structure does not change,  its age does. The process ages and when dividing, the new stem cell inherits its age. While   zygote age  = 0, stem cell age > 0, and it rises with every division, which bears on the CA-2 structure. This phenomenon is called determination. When the real  zygote divides, each of its progeny may differentiate into a separate organism. As embryo grows the stem cell loses this capacity, and may differentiate only into an organ.Later on the potential of its stem cells to differentiate narrows, and at birth stem cells are determined to differentiate into specified  tissues.

Further reading: Streaming tissues

restoreparams[1,1,1]; restoreparams[2,2,1]; If stateno[[1]]==46, killca[2],  maxage+=4; dying[2,maxage, 0]; go [100];

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