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Comment by lend000 | Hacker News Reader

There was an article on HN a few months ago claiming every neuron in a human brain is genetically unique (my interpretation was that this was due to random errors). So essentially, you won't be able to find a single cell to clone a multicellular organism with any accuracy -- you would need to take a large number and average out the variation to get a reliable estimate of the original zygote's DNA. (And perhaps pump of telomere length as well, or make any other adjustments that would happen consistently across cell divisions).

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The unique mutations in your brain and immune system too are induced during development. The body needs variation in neurons so they can recognize themselves millimeters away and not connect with themselves. And it needs immune cells that recognize a wider variety of proteins than could be encoded directly in DNA. So somehow mutations are induced in specific genome regions in the brain and immune system.

Which isn't to say that mutations don't play a large role in other cells. The average child has at least one mutation but usually they don't do much. Well, doesn't do much or means the zygote is totally nonviable and so never results in a pregnancy. Having children when you're older will tend to increase the number of mutation, especially for men where their gametes are produced throughout their lives. A cell from, say, someone's skin will tend to have even more mutations but that's a quantitative thing rather than a qualitative one.

> The body needs variation in neurons so they can recognize themselves millimeters away and not connect with themselves.

Do you have a source for this? How would a neuron with a mutation be any different from the outside in terms of its axons?

Sorry, no. I was really fascinated that the brain had all this genetic diversity and eventually I was able to ask a neuroscientist at a party why it was there.

Cells’ uniqueness is explained by epigenetic. And as already said, this problem could be eliminated. You can take a new borned baby stem cells with zygote's DNA almost in every clinic nowadays. The main problem is that almost all finding are banned in this field. I guess modern countries are incompatible with cloning. It is too game changing.

> Cells’ uniqueness is explained by epigenetic.

No, I think cell differentiation is a completely different topic -- gene expression/inhibition and cell specialization has nothing to do with random errors to DNA, as far as I understand. So the problem is not actually solved at all. Especially since we are not usually trying to clone babies, whose stem cells would have incurred less damage.

Yes, I meant “random errors to DNA”. I don’t think they have quantum nature. So the problem is how good you can reproduce environment. I can see no obstacles why we can’t solve this problem. Baby stem cells are freezing for future use. It is real. it happens now. BTW, you can get exact DNA copy in case of IVF if you think it is crucial.

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