Symmetry in dynamic biological organization
This chapter deals with the question of how millions of molecules can be spatio-temporally organized in morphogenetic fields such that form arises in developing organisms at macroscopic scales extending from micrometres to millimetres — the characteristic lengths over which biological form is generated. At present, the predominant view is that of molecular biologists: the genetic programme metaphor and the implicit belief that the ultimate explanation of morphogenesis resides in the molecular realm, i.e. that all relevant information is encoded in the DNA. Thus, a basic implication of the genetic programme metaphor is that genes, via their products, determine macroscopic biological form. One should not forget, on the one hand, that genes only encode proteins that participate either as catalysts or effectors of metabolic fluxes or as structural elements such as cytoskeleton or membrane components (Chapter 11). On the other hand, the spatio-temporal scaling of molecular events is very different from that corresponding to morphogenesis in embryonic fields. Thus, the activity of thousands of molecules in developing systems is somehow subjected to spatiotemporal coordination.
KeywordsFluctuate Asymmetry Percolation Cluster Anterior Pole Phenomenological Coefficient Cytoskeleton Component
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