Originally posted by scilosopher
SInce evolution occurs on the level of the organism one clearly has to start thinking about how the elemental building blocks of genes fit together into functional systems.
this might be pointless because development is highly modular. functions can be adapted and switch and to accomplish the same structure different modules can be used in quite related species. I was looking myself at the stem cell compartment of the tooth in mice and voles and noticed for instance that the WNT ligands (one of the major signaling families) are not expressed similarly. This project has never reached an advanced status but possibly different WNTs take over the function of another WNT in the same tooth in vole and mouse. Or because I actually did not find any subsitute for certain patterns yet, another signaling pathway may have taken over the role completely. And that to create a tooth which is the same in shape and function in both instances. This is just a personal example, but I am sure it is not the only one.
What is therefore then the point in looking at elemental building blocks of genes? They don't necessarily exist in this fashion. A similar functional system can arise by different developmental means, using different genetic 'blocks'.