
700,000-Year-Old Horse Found in Yukon Permafrost Yields Oldest DNA Ever Decoded - salemh
http://westerndigs.org/700000-year-old-horse-found-in-yukon-permafrost-yields-oldest-dna-ever-decoded/
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marquis
I love seeing modern 2-legged dinosaur depictions with feathers. I wondered
why, growing up, everyone didn't see that they were just giant birds with
teeth and weird little arms.

~~~
Samuel_Michon
When I was growing up, I thought crocodiles were the closest thing to
dinosaurs. I’m fairly sure that’s what I was taught in school. Then came all
the drawings of dinosaurs with feathers and my mind was blown when I read that
birds are actually more closely related to dinosaurs than crocodiles are.

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4ad
> the half-life of a DNA molecule is estimated to be about 521 years. By this
> reckoning, even under the best conditions, DNA could remain intact for no
> more than 6.8 million years.

I just love how they skip inferences...

~~~
VLM
If its an exponential decay process, as it supposedly is, then its more of a
statistical game where the median helix would have cracked into 1 base pair at
6.8Myr.

That would really suck if you only had one single helix to work with. However
I'd think theoretically given an infinite amount of genetic data (unlikely)
you could analyze every molecule in the sample separately and then put it back
together.

There's a radiation analogy... if you've got a speck of Co-60 of a certain
almost infinitely small size, its not too hard to do the math to prove that
after 1M years theres less than one atom left of Co-60. Say you want a 1 Kg
pile of Co-60 thats 1M years old. Yes, indeed, it is very true that if you
start with exactly and only one speck of Co-60 the odds exceed 50% chance that
there will be less than one atom left. The solution is simple, start with a
bigger piece than an infinitely small speck and use a lot more than one speck.

This isn't a silver bullet, being exponential, if I were not so lazy I could
work out that if you wanted the DNA from the first known life on the planet,
you'd need a multiple of the entire mass of the universe as a starting sample
size or something crazy like that.

Just saying if you want 6.80001 Myr DNA its not impossible its just going to
be a huge expensive PITA compared to existing techniques for stuff merely 100
years old.

The guy who divided 6.8e6/521 I think is trying to tell you how many base
pairs long an average DNA helix probably would be, I think, sorta? So the
average 1/2 life of a base pair is 521 years, and half of an entire helix is
6.8M years.

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new299
"Just saying if you want 6.80001 Myr DNA its not impossible its just going to
be a huge expensive PITA compared to existing techniques for stuff merely 100
years old."

That's kind of an interesting problem. I wonder how much material you'd need
to get decent coverage of a averaged sized organism (few gigabases) given the
decay rates they calculated.

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imahboob
Where can I read more about "Single Molecular Sequencing", looks very
interesting..

~~~
njbooher
Based on the sequencing read archives for that publication[1], it looks like
they used Helicos[2]. PacBio[3] is another form of it.

[1]
[http://www.ncbi.nlm.nih.gov/sra?LinkName=pubmed_sra&from_uid...](http://www.ncbi.nlm.nih.gov/sra?LinkName=pubmed_sra&from_uid=23803765)

[2]
[http://en.wikipedia.org/wiki/Helicos_single_molecule_fluores...](http://en.wikipedia.org/wiki/Helicos_single_molecule_fluorescent_sequencing)

[3]
[http://en.wikipedia.org/wiki/Single_molecule_real_time_seque...](http://en.wikipedia.org/wiki/Single_molecule_real_time_sequencing)

~~~
new299
The Helicos stuff would have to be pretty old, they've been effectively out of
business for some time (having filed for bankruptcy in 2012).

The paper suggests they mostly used Illumina, with one guy using Helicos:

"J.S. did ancient and modern DNA extractions and constructed Illumina DNA
libraries for shotgun sequencing"..."X.W. did Illumina libraries on donkey
extracts"..."A.S.-O. performed Illumina sequencing for the Middle
Pleistocene".."Ji.M. and X.W. performed Illumina sequencing for the Middle
Pleistocene and the donkey genomes at BGI".."J.F.T. headed true Single DNA
Molecule Sequencing of the Middle Pleistocene genome"

It's worth noting that while Illumina sequencing isn't true single molecule,
you are getting a read signal from a single fragment of DNA.

