Massive, and horrendously obfuscated. If a programmer came up with designs akin to what evolution has produced, we wouldn't know whether to fear him for his genius or institutionalize him for his madness. In any case, he would likely get fired.DNA research is just a form of reverse engineering. We have a massive executable and are trying to decode it.
Am I correct that the DNA does not determine the shape of the organism, but DNA just codes for proteins, which determines certain traits? In many experiments scientists inject the DNA of the glowing jellyfish that makes them glow into another organism, they now make the protein that glows but they do not turn into jellyfish.
DNA determines everything (if you include mitochondrial DNA, which is separate from the chromosomes in the nucleus, and if you exclude bacteria which have RNA instead of DNA). HOX genes are the ones that determine major body areas; some of them are similar in organisms as different as insects and humans.
An error in this kind of gene is how you get flies with legs where antennae should be, and that sort of thing.
In the jellyfish example they are not injecting ALL of the jellyfish's DNA, only the small strand that is related to the glowing.
As for the reason behind DNA order:
(I briefly considered the idea of being a geneticist when I first went to college)
Proteins behaviors and structures of multiple proteins (like hemoglobin, the protein complex responsible for transporting oxygen in your blood) are due to their 3d structure, which is created according to a folding pattern, and that folding pattern is due to the order in which the amino acids are attached to the protein's AA chain. Hydrophyllic vs hydrophobic sections will cause certain 3d structures as the protein folds up. This is why the order of DNA encoding is so important, because proteins do just about everything important in our cells.
This is also why prions are so freakin' scary: they misfold proteins. No cell functions for you, thanks.
HOX genes are the ones that determine major body areas; some of them are similar in organisms as different as insects and humans.
Just thought I'd add onto this point a bit:
Since all cells in the body contain the same HOX genes, there must be some external factor influencing which cells express specific HOX genes. One factor that controls the expression of the HOX genes is the presence of certain chemicals; in the embryonic environment, there is typically a gradient of chemical concentrations that gives the embryo a general idea of which directions are "up", "forward", "right", and so on. Once the cells begin differentiating, they produce additional chemicals that further refine their specialization.
