Within an embryo, several processes play out at the cellular and tissue level to create an organism.
Almost all animals undergo a similar sequence of events during very early development, a conserved process known as embryogenesis.
Studying model organisms provides information relevant to other animals, including humans.
[7][8] This technique of fate mapping is used to study cells as they differentiate and gain specified function.
As embryos mature, more complex fate determination occurs as structures appear, and cells differentiate, beginning to perform specific functions.
Determination is followed by differentiation, the actual changes in biochemistry, structure, and function that result in specific cell types.
[19] This type of specification results from cell-intrinsic properties; it gives rise to mosaic development.
The cell-intrinsic properties arise from a cleavage of a cell with asymmetrically expressed maternal cytoplasmic determinants (proteins, small regulatory RNAs and mRNA).
Autonomous specification was demonstrated in 1887 by a French medical student, Laurent Chabry, working on tunicate embryos.
In cases where the external or stimuli that would cause asymmetry are very weak or disorganized, through positive feedback the system can spontaneously pattern itself.
Once the feedback has begun, any small initial signaling is magnified and thus produces an effective patterning mechanism.
As a result, the removed tissue was autonomously specified since the cell was not able to make up for the missing part.
Only the cells exposed to the signal are induced to follow a different developmental pathway, leaving the rest of the equivalence group unchanged.
As there are no cell boundaries in the syncytium, these morphogens can influence nuclei in a concentration-dependent manner.