Does the human body have a blueprint for how it should look and function at certain stages of growth?

By blueprint I mean a map of everything that a person should look and function like, barring diseases, mutations, or any other abnormality that would factor into how a person's body looks and functions as it develops. If such a blueprint exists, does the body keep it stored in the form of DNA, some digital-like information in the brain, or something else?|||DNA is not like a blueprint: a better analogy is that it is like a recipe.





A blueprint contains a direct, part-for-part representation of the final product. If DNA were like a blueprint, then there should be such a representation of the physical structure of a human heart, for example, in it somewhere ... there isn't.





A recipe contains a series of instructions that direct a progressive process through steps - the early ones not resembling the final product much at all - that unfolds to produce, at the very end, the final product. That is a better analogy for how DNA stores the information for making a human heart.














Embryonic development itself is a very complex process. Information also comes from the developing embro itself, in that a cell receives information from its surroundings. And based on that external information, the cell modifies expression of its genes.





Morphogens are diffusable molecules involved in development by altering cells' gene expression. Morphogens have a concentration gradient: their concentration is highest near the cell(s) that secrete them and tapers off as distance from the source increases. Cells at different distances from the source are therefore exposed to different levels of the morphogen, and can therefore respond differently to its presence. And there are many different morphogens. Thus, cell X can be in an area of high concentration for morphogen A, a low level for morphogen B, and intermediate level for morphogen C, and outside the boundary of morphogen D, whereas cell Y can have a different combination. Receiving different information from multiple external sources leads to distinct patterns of gene expression.





This morphogen-produced develompental information is not encoded directly in the genome: it unfolds as development progresses. For example, there's no gene timer sitting next to gene X that ticks off 32 hours and then switches gene X on, then when it hits 100 hours turns gene X off. Gene X is turned on when and if the cell receives the proper external stimuli (from a morphogen, for example), and is turned off in a similar manner.|||It's not really a blueprint, it's more like a very detailed recipe - a list of what to do at each step. Grow cells in this direction until the arm is yay long, then split off into fingers, then grow a bit more, stop. Cells at end should become fingernails, put an elbow about halfway down, etc. There's no real overall "Plan" per se. It's a mix of timed signals, what a cells' neighbours look like, and chemical gradients that actually determine what a body ends up looking like. It's actually a lot more like baking a cake than building a house - mix this, stir, bake etc, but nowhere does it tell you what the finished product looks like.





Sometimes one of the instructions gets misread, and this leads to a malformation even if there are no mutations. Unless it's lethal, the body just keeps developing despite the mistake.





The cells "read" the instructions via protein receptors, which then relay information to the cells, which then express other proteins which cause development down a certain path, as well as proteins that tell its neighbours what that cell is up to so they know what to do as well. This information is stored exactly where all other protein information is stored, as genes in the DNA.