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DNA doesn't make a copy of itself, the cell makes a copy of the DNA. DNA doesn't really do anything, it requires RNA and proteins to actually do anything.
by enkid 3y ago
DNA doesn't make a copy of itself, the cell makes a copy of the DNA. DNA doesn't really do anything, it requires RNA and proteins to actually do anything.
- rebolek 3y agowell, quine program doesn't do anything by itself too, you need computer and electricity for it to work
- enkid 3y agoThere's a definitional problem here. Would a book with instructions for how to order additional copies be a quine? What's the difference? I don't know exactly.
- mtlmtlmtlmtl 3y agoI guess the right question to ask about DNA is, does it contain all the instructions required to produce a copy of the DNA itself? DNA translation involves a bunch of RNA, sure. But DNA copying is mostly done by DNA polymerases, which are typical peptide based proteins encoded in the DNA itself, right? So in a real sense, the DNA contains the blueprint for the machinery to copy the DNA itself, but not the instructions for building that machine from the blueprint, the same way a software quine doesn't necessarily include the source code for a compiler. Definitely a definitional problem, but that's my shot at resolving it a bit. Then again, DNA polymerase is not perfect, and DNA is not immune to single nucleotide changes having a real effect, so it's only a quine in the "spherical cow" way of looking at it anyway. But it's certainly the most "quinish" thing in nature that I can think of.
- enkid 3y agoI just don't think it's accurate to say DNA has instructions in the same way a computer does. It's more like a recipe for a chemical reaction. If we expand the definition of a quine away from being self reproducing code and to self reproducing chemical reaction, it seems like things like crystalization or fire could be considered a quine.
- mtlmtlmtlmtl 3y agoI actually like that. But I may have been a bit unclear about my mapping of computer and biology terminology to this question. I tend to think of a computer programs as being mathematical machines, and proteins as being molecular/chemical machines. Motor proteins "walking" along microtubules is the most vivid example of this. I'm sort of torn between both worlds here, honestly. I like both perspectives. Viruses especially have a very quinish quality to them in that they're stripped down to just enough stuff to get a host cell to make more viruses.
- enkid 3y agoI like the virus as quine analogy much better than generic DNA as a quine, personally. Seems much more meaningful.
- PartiallyTyped 3y agoThe program doesn't make a copy of itself, the runtime makes a copy of the program. Program doesn't really do anything, it requires runtime and cpu to actually do anything.
- Karellen 3y agoDNA includes instructions for how to build all the machinery needed to make a copy of itself, including the surrounding cell, and RNA, and proteins, and the organism that is capable of gathering food/fuel to obtain the all the raw materials to build everything.
- enkid 3y agoNo it doesn't, it holds a recipe for creating proteins under specific chemical and biological conditions. If you put human DNA in a chicken egg, it wouldn't hatch a human.
- Karellen 3y agoAnd if you write a quine computer program on a piece of paper, it won't create a copy of itself further down the page. Or if you put a fully-functional cell in the vacuum of space, or the heart of a star, it won't replicate either. All replicators need a suitable environment to replicate in. The fact that inhospitable/non-viable environments exist does not negate the fact that they are actually replicators.
- tedunangst 3y agoIf you build a cell from only eukaryote DNA instructions, it won't have any mitochondria and be unable to copy itself.
- Karellen 3y agoMitochondrial DNA is still DNA. Symbiotic replicators that rely on the presence of each other to reproduce (like cycles of quines?) are also still replicators.
- tedunangst 3y agoI think also the Golgi apparatus has no DNA. You can't build one if you don't have one. But apparently we're still not sure where it comes from.