3 ms·

DNA completely decays after at most 1k years

by cft 5y ago

busymom0 5y ago
Is that true if it was frozen for the entire time?
- steve_adams_86 5y ago
  Where would something have stayed frozen for ~65M years? Not a rhetorical question so much as a follow up. I don’t know the answer to your question.
  - busymom0 5y ago
    Mostly asking a hypothetical question really. Like there have been Giant camel fossil found in Arctic: https://www.bbc.com/news/science-environment-21673940 https://www.bbc.com/news/science-environment-21673940
Sniffnoy 5y ago
You're off by at least an order of magnitude there; we have DNA samples from well further back than that, such as from Neanderthals and from mammoths. But no, it doesn't last long enough to get DNA samples from dinosaurs. I don't know the area well enough to give a good figure, but 1 million years seems to be an upper bound from what I can find quickly.
mkl 5y ago
DNA's half life has been estimated at 521 years [1] in moderate temperatures, so after 1k years a quarter of it would still be left. That must depend on the conditions though. DNA 500,000 years old has been found in ice cores (presumably a higher half life there, since of e.g. the 3 billion base pair human genome, 3e9/2**(500e3/521) ≈ 3.8e-280 would be left after that time with that half life). [1] https://www.popsci.com/science/article/2013-02/whats-half-life-dna/ https://www.popsci.com/science/article/2013-02/whats-half-li...
- credit_guy 5y ago
  A DNA molecule is very long, it has of the order of 1 billion nucleotides. You don’t need entire molecules to do the sequencing, just segments. Even if you had the entire molecules, you would start by splitting them up [1]. If you can retrieve enough segments, you might try some sort of Bayesian inference. You start with the DNA of the common ancestor of reptiles and dinosaurs (and therefore birds). You don’t know what it was, but you know that it evolved into the current reptiles and birds via random mutations followed by adaptive selections. You get a posterior for it, then you use it as a prior for the DNA of the dino for which you have sequenced a number of segments. [1] https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/biotechnology/a/dna-sequencing https://www.khanacademy.org/science/ap-biology/gene-expressi...
vixen99 5y ago
A classic counterexample is "Scientists took 166 bone samples from 151 mummies, dating from approximately 1400 B.C. to A.D. 400, extracting DNA from 90 individuals and mapping the full genome in three cases." as reported (for instance) on https://edition.cnn.com/2017/06/22/health/ancient-egypt-mummy-dna-genome-heritage/index.html https://edition.cnn.com/2017/06/22/health/ancient-egypt-mumm...

DNA completely decays after at most 1k years

by cft 5y ago

DNA completely decays after at most 1k years

busymom0 5y ago

Is that true if it was frozen for the entire time?

steve_adams_86 5y ago
Where would something have stayed frozen for ~65M years? Not a rhetorical question so much as a follow up. I don’t know the answer to your question.
- busymom0 5y ago
  Mostly asking a hypothetical question really. Like there have been Giant camel fossil found in Arctic: https://www.bbc.com/news/science-environment-21673940 https://www.bbc.com/news/science-environment-21673940

Sniffnoy 5y ago

You're off by at least an order of magnitude there; we have DNA samples from well further back than that, such as from Neanderthals and from mammoths. But no, it doesn't last long enough to get DNA samples from dinosaurs. I don't know the area well enough to give a good figure, but 1 million years seems to be an upper bound from what I can find quickly.

mkl 5y ago

DNA's half life has been estimated at 521 years [1] in moderate temperatures, so after 1k years a quarter of it would still be left. That must depend on the conditions though. DNA 500,000 years old has been found in ice cores (presumably a higher half life there, since of e.g. the 3 billion base pair human genome, 3e9/2**(500e3/521) ≈ 3.8e-280 would be left after that time with that half life). [1] https://www.popsci.com/science/article/2013-02/whats-half-life-dna/ https://www.popsci.com/science/article/2013-02/whats-half-li...

credit_guy 5y ago
A DNA molecule is very long, it has of the order of 1 billion nucleotides. You don’t need entire molecules to do the sequencing, just segments. Even if you had the entire molecules, you would start by splitting them up [1]. If you can retrieve enough segments, you might try some sort of Bayesian inference. You start with the DNA of the common ancestor of reptiles and dinosaurs (and therefore birds). You don’t know what it was, but you know that it evolved into the current reptiles and birds via random mutations followed by adaptive selections. You get a posterior for it, then you use it as a prior for the DNA of the dino for which you have sequenced a number of segments. [1] https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/biotechnology/a/dna-sequencing https://www.khanacademy.org/science/ap-biology/gene-expressi...

vixen99 5y ago

A classic counterexample is "Scientists took 166 bone samples from 151 mummies, dating from approximately 1400 B.C. to A.D. 400, extracting DNA from 90 individuals and mapping the full genome in three cases." as reported (for instance) on https://edition.cnn.com/2017/06/22/health/ancient-egypt-mummy-dna-genome-heritage/index.html https://edition.cnn.com/2017/06/22/health/ancient-egypt-mumm...