DNA is the genetic information holder for life. It determines the sequences of amino acids that are strung together into polypeptides, eventually proteins be they enzymes or whatever.
What I want to know is, how do you get the complicated structure that is a person, a plant, a mushroom, whatever, from this information?
Does the sequence and quantity of the proteins encoded in the genome somehow happily fall into place as a human?
Is there extra encoding in the DNA that serves as a sort of blueprint as opposed to just the component parts?
Do scientists even have conclusive evidence any particular way?
Development of an organism from a single cell is an intensely studied part of biology. It’s an immensely complex process for something like a human, but basically, it does indeed all come from the DNA. Proteins (encoded by the DNA) regulate every step of the process. As cells divide, they become differentiated into different tissue types. Shoot. It’s really way too complicated to get into. But yes, it’s proteins that do the job.
I’m not sure what you mean by blueprint DNA. There are regulatory sequences in the DNA that affect the expression of various genes. Hell, pretty much every gene is regulated in some way. Generally, there will be a protein that binds the regulatory sequence and turns a gene on or off.
As for evidence, yes, there’s plenty. It’s abundant. In the case of the worm C. elegans, scientists know the origin of every single cell in the adult worm. They have traced out exactly each cell division. They know the whole process from start to finish.
As Smeghead said, this is way too complicated to get into. Try searching around for info on “developmental biology” (dev bio). There should be a fair amount of sites floating around, but I don’t have the time to search just now.
Or alternatively, just pick up a biology textbook.
Any good intro to bio text should cover your questions 1 (look under genetics, transcription, and translation), 3 (look again under genetics, for regulatory sequences and such in DNA), and 4 (the answer is yes, and a good text should have examples of some of the work that established DNA -> RNA -> Protein as the ‘Central Dogma of Molecular Biology’).
For your second question, humans are defined by their genome and its products… it’s not a matter of “happily falling into place.”