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Could you not produce viable samples by collecting multiple copies of the DNA and overlapping them, thus removing the errors that would likely happen at random

by giarc 11y ago

Could you not produce viable samples by collecting multiple copies of the DNA and overlapping them, thus removing the errors that would likely happen at random locations?

noir_lord 11y ago
> Better statistical techniques will push this bound That's what he meant by statistical techniques, we don't currently read a full "stream" even with brand new DNA, we smash it to bits then read those and have the computers put them back together. At a certain point though what's left is too garbled or in too small sequences so that there isn't enough overlap that you can't put humpty back together again :).
searine 11y ago
Not likely. Dude to the chemistry of nucleotides, they can degrade in a particular pattern that obscures the ancestral allele. For example the deamination of cytosine to thymine can leave us with an ambiguity in what in our read for the correct nucleotide is. Was it thymine? Or was it cytosine that degraded to thymine? That means for literally 50% of the genome we have a huge ambiguity and few ways to tell what it really is. We can use the ancestral allele from a nearby extant species, but then we miss out on all the extinct variation (which is the important stuff). We can try to increase coverage of the ancient genome to capture loci where cytosines haven't deaminated, but thats tough for a dozen reasons, and in the end you'll still have no confidence in 25% of the genome. We can get very close to a full ancient genome, but never 100%. Maybe through transgenics, selective breeding, and ancient sequencing we can re-create ancient species, but we will never make them exactly as they once were.
- meric 11y ago
  we will never make them exactly as they once were And maybe that could be good enough and better than not doing it at all...
mehwoot 11y ago
Yes, but with a half life of 500 years, the amount of information you have halves every 500 years you go back. At some point there just isn't enough information to go viably go back further.

by giarc 11y ago

Could you not produce viable samples by collecting multiple copies of the DNA and overlapping them, thus removing the errors that would likely happen at random locations?

noir_lord 11y ago

> Better statistical techniques will push this bound That's what he meant by statistical techniques, we don't currently read a full "stream" even with brand new DNA, we smash it to bits then read those and have the computers put them back together. At a certain point though what's left is too garbled or in too small sequences so that there isn't enough overlap that you can't put humpty back together again :).

searine 11y ago

Not likely. Dude to the chemistry of nucleotides, they can degrade in a particular pattern that obscures the ancestral allele. For example the deamination of cytosine to thymine can leave us with an ambiguity in what in our read for the correct nucleotide is. Was it thymine? Or was it cytosine that degraded to thymine? That means for literally 50% of the genome we have a huge ambiguity and few ways to tell what it really is. We can use the ancestral allele from a nearby extant species, but then we miss out on all the extinct variation (which is the important stuff). We can try to increase coverage of the ancient genome to capture loci where cytosines haven't deaminated, but thats tough for a dozen reasons, and in the end you'll still have no confidence in 25% of the genome. We can get very close to a full ancient genome, but never 100%. Maybe through transgenics, selective breeding, and ancient sequencing we can re-create ancient species, but we will never make them exactly as they once were.

meric 11y ago
we will never make them exactly as they once were And maybe that could be good enough and better than not doing it at all...

mehwoot 11y ago

Yes, but with a half life of 500 years, the amount of information you have halves every 500 years you go back. At some point there just isn't enough information to go viably go back further.