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So there are often articles about cloning from a small piece of tissue etc.

My question is (two actually) Is the Complete information about entire organism's structure stored (as in duplicated) all over the body? And is everything actually stored/based on DNA information, such as number of hairs you have including their position and texture. That would be a lot of information, I mean just taking hair as an example and its quantity and position, but there are also things about every aspect of structure, from bone composition, to position of organs, veins etc. None of it is random (ignoring mutations aspect) and all of it has to be "programmed" in initially. How can this be possible when the number of specifications is so huge?

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The common phrase I've heard is "DNA isn't a blueprint, it's a recipe". More specifically, the nucleotides in DNA correspond to which proteins get made (coding DNA) and when and where (regulatory DNA). Just like a recipe doesn't specify the exact color of a cake or the position of each raisin, but does say "cook the cake for this long" (which will, in interaction with the heat of the oven, determine its color) or "put in this many raisins, at this general point in this general area", DNA doesn't contain the exact information of how you end up looking (hence why identical twins aren't really identical), but it does say how to make you how you are.

It also illustrates how much has to be "programmed" initially; how we are really needs to be understood as an interaction between DNA and the environment through the process of development, just as you can't completely understand a cake just from the recipe, you also need to know how chemistry and physics cause the things in the recipe to have the effects that they do. A lot of what goes on in development is cells growing, changing or dying depending on the chemical environment they're in, which includes what their neighboring cells are. The information in DNA basically consists of affecting that via what proteins get made when and where during development.

As for whether complete information about the entire organism's structure is stored all over the body, yes and no (but mostly yes). Yes, by default every cell in your body inherited its whole genome from the original zygote that started things, and you can indeed in theory clone a whole person from many random cells in the body. However in practice it depends on the cell: some cells lose their nucleus entirely, like red blood cells, so of course they don't contain the body's whole genome. Other cells could theoretically multiply or eliminate certain genes in a similar way as they specialize for the specific task they need to do, meaning they won't end up with the same genes as all the other cells in the body, but this isn't thought to be a common phenomenon especially in humans (cells will vary more in the expression pattern of their genes without necessarily changing the DNA sequence itself). This is also ignoring the ordinary mutation rates in DNA as the cell divides, which will yield differences between different cells of a given body even without that being a deliberate process. Hence cancer !

Some references on the possible variations of DNA in somatic cells (i.e. not ova or sperm)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497787/

It is commonly assumed that all healthy cells that arise from the same zygote possess the same genomic content, with a few known exceptions in the immune system and germ line. However, a growing body of evidence shows that genomic variation exists between differentiated tissues.

Elimination of actual DNA in nematodes and lampreys :

https://www.ncbi.nlm.nih.gov/pubmed/23123092

https://academic.oup.com/mbe/article-abstract/33/9/2337/2579241/Characterization-of-Somatically-Eliminated-Genes?redirectedFrom=fulltext

Quote from the first abstract:

Chromatin diminution is the programmed elimination of specific DNA sequences during development. It occurs in diverse species, but the function(s) of diminution and the specificity of sequence loss remain largely unknown.

I have found no mention of it happening in humans however.

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  • $\begingroup$ Thank you for definitive answer to my first question, makes it clear now. However regarding the 2nd question (blueprint-related) I'm still not 100% clear (probably because I didn't elaborate enough). Using computer terminology, we can write a detailed Instruction that performs exact task, or we can use/rely on a Library that is "known" to accomplish a particular task. This library being Environment, the instruction would be Environment(Plant Hairs in area X). Two ways -- same result. To create the organism, DNA (or something else) must know how to use the Library. Please explain :) $\endgroup$ – Emil Mar 2 '17 at 7:37
  • $\begingroup$ I'm not sure quite what you mean by "know how to use". The computer analogy is a terrible one, but I'll try and explain as best possible in the frame you're starting from. Do you mean "know how to use" as in "is compatible with" (uses the correct syntax, etc) or as in "is aware of the adequation of the library to the program's ultimate goals" (uses a scipy library for science calculations, etc) ? In the former case, the library is the laws of physics and chemistry, DNA follows those by default because it exists in the world. In the latter case (...) $\endgroup$ – Oosaka Mar 2 '17 at 8:57
  • $\begingroup$ the "instructions" in DNA (also not a good analogy btw) don't come from an ultimate goal; it just so happens that various proteins being made at various points has an effect on the final organism (because chemistry and physics), and when that effect promotes the final organism's reproductive success the originating DNA pattern spreads through the population, until all organisms have it and it looks like it was put there on purpose to have that effect (which in a way it was for a certain understanding of "purpose": the effect had a causal influence on why that instruction is there now). $\endgroup$ – Oosaka Mar 2 '17 at 9:02
  • $\begingroup$ Still not 100% clear. Lets say initially these proteins started out at various positions and now we have a particular organism. Whatever the physics/chemistry may be, in order to survive, DNA needs to accommodate for these things. The closer the match the better success rate. Lets take an eye for example and try to design it in a biological 3D printer (if one existed) We need 1) "blueprint" or some sort of "instruction set" and 2) Something that has the ability to transform/delegate it into "design" stage. Otherwise, why would cells just stick together forming an organ of such complexity? $\endgroup$ – Emil Mar 7 '17 at 15:16
  • $\begingroup$ @Emil the eye isn't designed in a 3D printer. Organisms are self-assembling. And there isn't a clear division between "blueprint" and "assembly", just like the brain doesn't have a clear division between "software" and "hardware". DNA isn't the passive repository of the information to build something; it is an active part of the functioning of the cell, given it's part of the production of proteins. And cells split and stick together depending on what proteins they're secreting in their membrane, and that's determined on which genes are expressed. $\endgroup$ – Oosaka Mar 7 '17 at 15:37

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