DNA has a 521-year half-life

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Genetic material can’t be recovered from dinosaurs — but it lasts longer than thought.


Few researchers have given credence to claims that samples of dinosaur DNA have survived to the present day, but no one knew just how long it would take for genetic material to fall apart. Now, a study of fossils found in New Zealand is laying the matter to rest — and putting an end to hopes of cloning a Tyrannosaurus rex

After cell death, enzymes start to break down the bonds between the nucleotides that form the backbone of DNA, and micro-organisms speed the decay. In the long run, however, reactions with water are thought to be responsible for most bond degradation. Groundwater is almost ubiquitous, so DNA in buried bone samples should, in theory, degrade at a set rate.

Determining that rate has been difficult because it is rare to find large sets of DNA-containing fossils with which to make meaningful comparisons. To make matters worse, variable environmental conditions such as temperature, degree of microbial attack and oxygenation alter the speed of the decay process.

But palaeogeneticists led by Morten Allentoft at the University of Copenhagen and Michael Bunce at Murdoch University in Perth, Australia, examined 158 DNA-containing leg bones belonging to three species of extinct giant birds called moa. The bones, which were between 600 and 8,000 years old, had been recovered from three sites within 5 kilometres of each other, with nearly identical preservation conditions including a temperature of 13.1 ºC. The findings are published today in Proceedings of the Royal Society.

Written By: Matt Kaplan
continue to source article at nature.com

10 COMMENTS

  1. Why is it a gimmick? They claim that the main process of long-term decay is a first order kinetic process. This means the rate of decay is proportional to how much is left:  i.e. it has a half-life.

  2. Kurt75
    Why is it a gimmick? They claim that the main process of long-term decay is a first order kinetic process. This means the rate of decay is proportional to how much is left:

    First of all: the term is usually used in relation to radioactive decay.

    Second: As stated  @OP:twitter organic decomposition is not a single time-able  invariable process.  Unlike radio isotopes, this means it is only a very rough guide indicating a limit on the distance into the past where it is possible. It is not a method of dating.

    @OP:disqus To make matters worse, variable environmental conditions such as temperature, degree of microbial attack and oxygenation alter the speed of the decay process.

    Third: a few remaining random remaining molecules are not much use in deciphering a genome.  Unlike radio isotopes, tiny % traces from the distant past do not tell you much about such complex molecules, other than some organic molecules existed.

  3. I know this is trivial, but just for some light relief, this old song explains how they disappeared;

    No moa, no moa,
    In old Ao-te-aroa
    can’t get ’em
    They’ve et ’em
    They’re gone and there
    ain’t no moa.

    (Ao-te-aroa the Maori name for New Zealand)

  4. God creates dinosaurs.
    God kills dinosaurs.
    God creates man.
    Man kills God.
    Man creates dinosaurs.
    Dinosaurs eat man.
    Woman inherits the Earth.

    On a serious note. I’m saddened about the half life of DNA being so short. It would have been so cool to restore extinct species. Maybe it still might be possible to bring back a Mammoth ?

  5. Do we need functioning DNA or just a template to build from?

    You only need a template, but you need the template to be in a usable form.

    If, for example, your goal was to amplify and sequence a particular (know) locus,using a conserved flanking sequence, then you need at least a few DNA molecules where the intervening (unknown) sequence is intact.

    If your goal is to do whole genome sequencing then you need the template to be sufficiently unfragmented that you can get reads long enough that you can assemble into a genome sequence.  Some modern sequencing technologies use very short reads indeed (less than 100bp in some cases), but assembly can be difficult without a related genome sequence to build on.

    As such, factors such as the amount of starting template along with how much money you are prepared to throw at it (not to mention all the environmental variation described in the paper), are going to affect how far back in time you can get usable DNA samples.

    It would be really interesting to see the work replicated in a completely independent system.

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