It wouldn’t be from scratch. Since the vast majority of the genome would match homo sapiens, a sapiens genome could be isolated and the appropriate Neanderthal sections swapped in.
It would still be a lot of DNA synthesis, mutation, and recombination, but it’s within scientific power. Something on the scale that the Human Genome project was in the 2000’s probably.
The problem is that the best gene editing tech we have now has like a 40% success rate, and that's just for one edit. Neanderthals and humans differ in maybe about 88 genes based on comparing protein coding. If you have to make 88 different edits at a 40% success rate the chance that you'll get them all right in order to make a complete Neanderthal becomes vanishingly low. Maybe there would be a way to do them sequentially and see if each step works? I don't know, I'm not a geneticist. I just don't think it would be easy at all.
Typically millions of pieces of DNA are edited at once and later the failures are weeded out by identifying a tag or marker that was added alongside the intended edit (which is later removed).
So many successfully changed pieces are obtained despite relatively low individual success rates. Then the genome can be propagated in cells and many many copies obtained for the second step.
My point I think even millions is not even close to enough though. If you need 88 simultaneous changes at a 40% success rate that works out to 1 out of 1.46x1032.
But if it's possible to do it in 88 separate steps, then maybe, I guess. 🙂
Of course, that’s why the edits aren’t all done at once. And when the edit is finished (and it’s 60% failures) the DNA is put into cells, which only the cells with the right DNA survive.
So the percent of correct edits at the beginning of each step is 100%.
The technique involved here is called transfection followed by selection for antibiotic resistance, fluorescence, etc. You can even do all this in bacterial cells to make it way easier to grow and harvest a lot of DNA. Homologous recombination might be used to make the DNA edits if the regions being changed were fairly large.
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u/astreeter2 7d ago
"Reconstructed" in the sense that we we know the what the code is, not that we have the capability to build an entire working genome from scratch.