I've just picked up my notes from school when we were dealing with reproduction at biology class, and found out that during the growth of an embryo, there is a stage in which, in stead of just creating more and more cells, 'cellular differentiation' is initiated. In this phase, certain genes are activated, while others are deactivated, to force the cell into developing the features inscribed on those genes, which, in turn, specialise the cell, making it for example: a nerve cell, a skin cell, a cell of the liver or stomach, or any other cell of the human body (assuming it is a human embryo we're talking about).
The cells, in their pre-differentiating state, are called 'Stem Cells', and can be used, by chemical induction (see below) to create any specific type of cell, just like the regulation in the embryo (see below), which is why they are so prized and wanted in science. (Which is maybe why we don't know enough about this subject, as there are many people against stem-cell research, right? So logically speaking, if we were able to research stem-cells, we might figure out more about embryonic development, and maybe, just maybe, have this chapter of the religious debating history made to end )
Now then: Differentiation is done via the so-called 'regulation', or 'regulation of gene expression' (I love that term ), of which I haven't got very much knowledge, alas... The only thing I do remember about it is that this process is induced by something we Dutchies call 'chemical induction' (no idea how it's called in the lingua franca, however). In this chemical induction, genes are somehow activated by a certain change in the amount and type of chemicals present (I believe it were types proteines, but correct me if I'm wrong...)
And that's where I'll hop out of the picture... For I have no idea how ALL of the proteines and chemicals get there, or how they are created, or how they get at the right spot... The only chemicals I know are the ones that are secreted from the Chorda (the 'primitive/reptillian' vertebrae), these will make the cells above it differentiate into mesodermic stuff, which will become the 'neural tube' (or something... it's that nerve thing that goes through your vertebrae to which all the nerves connect... it's attached to the brain stem (lowest part of the brains)). So... That's one example, but I have no idea of the rest of the chemicals... who knows...
So: Any embryologists here? (is that even a word??? O_o)
P.S. I am but a humble 16-year old high school student, not an embryologist and might not know (or remember) the correct details. Therefore, there could be errors in the description above... It was just what I can remember about what I've learnt. So don't go hammer me when you've found a mistake a'ight? ^^
P.P.S. Gotta Love Science!!!
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