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Comment by marcosscriven | Hacker News Reader

I'm not sure if this is fair, but it strikes me as somewhat slapdash to take a sample right there in the field. Also, while there is red liquid, what's the chances it contains actual viable DNA, rather than what amount to DNA fragments and a bit of haemoglobin?

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With modern sequencing, are a large quantity of 'DNA fragments' sufficient for full nuclear genome replication?

edit: Make that two questions: one for 'full nuclear genome replication' and one for 'full nuclear genome sequencing'.

It actually is possible to recreate the full genome and sequence it from just fragments. In fact Craig Venter's strategy during the Human Genome Project used this idea. They made countless copies of the full genome, then fragmented each copy at different points. They then sequenced each fragment, since it's much faster to sequence short ones. After that they looked at all the overlaps in these fragments to create longer, continuos sequences.

When you sequence a new species (like when cannabis was sequenced last year) with a modern sequencing technique, you break up the large DNA strands into many small ones and then use a massive cluster to assemble the strands afterwards with statistical methods. It'll be more complicated here because you will have many varied samples with varying degrees of degeneration across different chromosomes, sequences, and samples but the basic concept is the same.

So how about for replication?

Have we developed the tech to go from mammal -> digital genome sequence -> physical replicated chromosome -> egg implanted with chromosome -> developmentally normal mammal -> fertile offspring, yet, or is that somewhere in the future?

No. That chain ends at the second step "digital genome sequence". In principle, we could synthesize a bunch of DNA strands corresponding to the genomic sequences and ligate them all together (although it would be absurdly expensive and laborious), but this would not constitute a chromosome. Eukaryotic chromosomes are organized in the nucleus by a huge variety of scaffolding and modifying factors (histones, etc.) into structures called chromatin. Recapturing this from sequence data is impossible, even in principle; the information is just not there. Indeed, understanding nuclear organization at a bunch of different leves is one of the big challenges of modern genetic research.

Worse: red blood cells contain no DNA, right? No nucleus. So they're depending on finding the much-scarcer white blood cells?

Yeah, that's true for mammals, which happens to be the case.

> I'm not sure if this is fair, but it strikes me as somewhat slapdash to take a sample right there in the field.

It makes sense to take a sample immediately and preserve it ASAP.

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