M. Møhl
Palaeogeneticist Morten Allentoft used the bones of extinct moa birds to calculate the half-life of DNA.
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 B1.
Diminishing returns
By comparing the specimens' ages and degrees of DNA degradation, the researchers calculated that DNA has a half-life of 521 years. That means that after 521 years, half of the bonds between nucleotides in the backbone of a sample would have broken; after another 521 years half of the remaining bonds would have gone; and so on.
The team predicts that even in a bone at an ideal preservation temperature of −5 ºC, effectively every bond would be destroyed after a maximum of 6.8 million years. The DNA would cease to be readable much earlier — perhaps after roughly 1.5 million years, when the remaining strands would be too short to give meaningful information.
“This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect,” says Simon Ho, a computational evolutionary biologist at the University of Sydney in Australia. However, although 6.8 million years is nowhere near the age of a dinosaur bone — which would be at least 65 million years old — “We might be able to break the record for the oldest authentic DNA sequence, which currently stands at about half a million years,” says Ho.
The calculations in the latest study were quite straightforward, but many questions remain.
“I am very interested to see if these findings can be reproduced in very different environments such as permafrost and caves,” says Michael Knapp, a palaeogeneticist at the University of Otago in Dunedin, New Zealand.
Moreover, the researchers found that age differences accounted for only 38.6% of the variation in DNA degradation between moa-bone samples. “Other factors that impact on DNA preservation are clearly at work,” says Bunce. “Storage following excavation, soil chemistry and even the time of year when the animal died are all likely contributing factors that will need looking into.”
- Journal name:
- Nature
- DOI:
- doi:10.1038/nature.2012.11555
According to the text, DNA decay varies according to factors such as presence of enzymes, microorganisms, water. As an example, bones of different species have different sizes, shapes and densities and this could in theory affect how the DNA inside interacts with water and microorganisms.Get more followers
Wow i really have to say this was an interesting read!
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Thanks for the great article on cloning and DNA – It's just a shame we won't be able to clone the T-Rex. I will always hold out hope though!
It seems absurd to be doing experiments of this type, although it reaches conclusions good as Simon Ho says: “This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect” mesas de hosteleria online
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If you want to find out some shocking information about dinasour DNA i recommend checking out David Icke's videos on youtube. His research is quite interesting to say the least. I recommend starting with his video "Human Race get Off your knees". It may take a little bit to get to the dinosaur area , but your life may never be the same after hearing his truth.
Melanie, from <a href="http://www.goldzc.com"> Silver Prices</a> Reports and <a href="http://thefinancedirectory.com/"> Siver Prices</a> Economic News.
Interesting article.This year will mark year 6 that a cadaveric stem cell tissue form has been commercially available in the USA. In 2012 approximately $155 million will have been spent on this tissue form. Over 1 million patients are walking around with hundreds of thousands of cc's implanted. Two of the largest tissue banks/processors; MTF & Allosource have been processing this tissue form for years. Almost every major spine center in the US uses this tissue form.
The assumptions in the 521 year half life number is that we are above freezing temperatures. so mammoth DNA has a different experience
there are arguments to make that frozen water would lengthen the half life (frozen water is not as chemically active) or shorten it (ice crystals shredding the DNA physically rather than chemically)
I'm not knowledgeable enough to guess if the frozen effect would save the DNA better or shred it even worse, but i think it is a valid to say that the half life would be a lot different if you are dealing with a corpse that was frozen at death and stayed that way in permafrost the entire thousands of years time before getting to a modern biotech lab
(from the second paragraph of the article) "...the nucleotides that form the backbone of DNA..."
[nitpick mode] Not quite. The nucleotides form the "rungs of the ladder" of DNA; the alternate deoxyribose and phosphate groups form the backbone.
[/nitpick mode]
Moving on, I too would like to see considerably more about the differences between the apparent (partial) survival of the ancient insect DNA (120+ Ma) and the moa DNA. Especially with the help of amber, is insect DNA more stable than avian DNA?
Great article guys, I found it a good read!
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What scientists really need to do is look further into what they call "junk DNA". Scientists that are alternative do not believe this is in fact "junk". But DNA that would associate us with higher life forms and once these "junk DNA" are activated then we as a collective could return to higher consciousness levels. Children that are currently being born with their junk DNA activated have paranormal capabilities such as being able to read in the dark with their toes. Seeing into the future and being telepathic and psychic.
That is my 2 cents. I'll get off my soap box now
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Which would be at least 65 million years old — “We might be able to break the record for the oldest authentic DNA sequence, which currently stands at about half a million years,”. The top songs to play at a funeral
I think that the temperature, atmospheric exposure, microbial content of soil, ect. should all have large impact on the rate of degradation. It seems like it would be very difficult to make a standard scale for this because of the enormous variability in conditions. uk business owners
This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect, says Simon Ho, a computational evolutionary biologist at the University of Sydney in Australia. Epic Followers
"The team predicts that even in a bone at an ideal preservation temperature of âˆथ ºC, effectively every bond would be destroyed after a maximum of 6.8 million years. The DNA would cease to be readable much earlier — perhaps after roughly 1.5 million."
While this might mean that dinosaurs won't ever be cloned, it is reassuring to know that there are many very interesting organizations that are well within this range, such as ground sloths, mammoths or Paraceratherium rhinos, which went extinct well within that range and include some of the largest known mammals in history.
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The DNA preserved in the amber should be a different case, as they are isolated from chemical, microorganism and moisture.yesRX
This means even in the relatively recent past, the amount of DNA we're looking at is pretty dang tiny. bail bonds san diego Part of the reason ancient DNA is so dang tricky is because the much of what you sequence is not actually what you're interested in – doubly so when you're sequencing something closely related to humans.
The 521 year half-life is if the DNA is exposed to water in typical situations, ITFA (in the article) they give an estimate for the best case situation...
The team predicts that even in a bone at an ideal preservation temperature of 5 C, effectively every bond would be destroyed after a maximum of 6.8 million years. The DNA would cease to be readable much earlier — perhaps after roughly 1.5 million years, when the remaining strands would be too short to give meaningful information.
“This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect,” says Simon Ho, a computational evolutionary biologist at the University of Sydney in Australia. However, although 6.8 million years is nowhere near the age of a dinosaur bone — which would be at least 65 million years old — “We might be able to break the record for the oldest authentic DNA sequence, which currently stands at about half a million years,” says Ho.
As other posters point out, the famous mammoth recreated from DNA was from about 10,000 years ago, much less than the 1.5 million year practical limit estimated by this research team.
Dr. David
I really think it may help you to review the definition of a half life. If you understand the implications of a half life you would understand why DNA would be found in custom t-shirts and other subjects far older then 521 years and you would understand essentially exactly how much DNA could be expected.
Scientist here (you can tell by my hat, and the fact that something like 90% of my comments on /. start with "I'm a biologist"). First, the DNA we get is from better preserved remains, which kicks the half life back further (It's in TFA, but not mentioned in the summary). There's still a 'deadline' around 7 MYA, where (allegedly) all the bonds would have pretty much been broken at that point – Frozen remains supposedly have a halflife around 158 kya. It's that dang phosphate backbone that's too willing to run off and go have reactions with any trallop of a molecule that wanders on by.
This means even in the relatively recent past, the amount of DNA we're looking at is pretty dang tiny. Part of the reason ancient DNA is so dang tricky is because the much of what you sequence is not actually what you're interested in – doubly so when you're sequencing something closely related to humans. For example, did some spot sequencing of ancient/historic polar bear remains, and had to toss out a chunk of the data we got back, as it was soil bacteria(/fungi/pollen) contamination. How do we know which is which? We had good scaffolds to align our bear sequences back up again, though not everyone is as fortunate as us.
In addition to being rare, what is left is fairly short. You can imagine if you start putting breaks in at random, your average length is going to start declining rapidly, and then level out at some small value that takes quite a while to get smaller. It'll get there, and given geologic time scales, a lot of what we want is that far back, but it'll take a while.
Finally, what isn't mentioned in this summary is that there was massive variance in the estimates of half-life. Supposedly only 40% of the variance in halflife was explained by age. Preservation, inter-lab differences, and good old fashioned luck probably contribute considerably to variance in half-life.
There are other factors too, but they're boring, and I should probably get work done instead of dragging out this reply.
(And to answer your latter question, Neanderthals have been sequenced whole genome, not just mtDNA).
I am sure that you will discover similar things in the future! It is nice that some people are interested to find more about dna.
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The DNA preserved in the amber should be a different case, as they are isolated from chemical, microorganism and moisture.
I think that saying that this is the half-life of all DNA is a pretty big assumption to make, seeing as environmental conditions have an enormous impact on the rate of degredation. Temperature, atmospheric exposure, microbial content of soil, ect. should all have a large impact on the rate of degradation. It seems like it would be very difficult to make a standard scale for this because of the enormous variability in conditions; it would be easier to take some DNA, stick it in various conditions in the lab, and watch it over the course of a long period of time than trying to derive it from bones which are not exposed to uniform conditions.
Also, 521 years is surely false precision, given that we're talking about 600 – 8000 years, suggesting 1-2 significant figures.
@Andersson, there are dozens and dozens of articles that have shown DNA can be isolated from organisms many millions of years old. It's preposterous to say that they have all been rejected. Please show me the retraction notices for each publication. And your citation is specific to DNA isolated from amber.
D Schlesinger:
Those articels are from the early 1990's and have since been rejected:
http://mbe.oxfordjournals.org/content/15/7/926.full.pdf etc.
If there would have been possible to isolate DNA that were 120 million years old back then, people would have made many such studies today.
@Owens, the article dismisses outright previous findings regarding DNA isolated from dinosaurs and other ancient organisms, an order of magnitude older than 500k years. And their statement that the oldest "authentic" DNA sequence is 500k years old is completely false.
@D Schlesinger the article certainly doesn't say that finding DNA older than 521 years is impossible. In fact it says it's likely that the widely accepted record for the oldest DNA recovered, of 500,000 years, could be significantly extended.
@Trainer Thank you, I am aware of the definition of a half-life, however the article (and subsequent articles reporting the same findings) are suggesting that finding DNA substantially older than 521 years is impossible. To quote the article above “This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect”.
Yet, dozens of peer reviewed publications show that not to be the case.
Flygon Trainer, Amy c is correct. The process is not entirely analogous to radioactive decay.
According to the text, DNA decay varies according to factors such as presence of enzymes, microorganisms, water. As an example, bones of different species have different sizes, shapes and densities and this could in theory affect how the DNA inside interacts with water and microorganisms.
Amy c, that would be like saying carbon 14 has a different half life depending on the organism it's housed in which is phenomenally unlikely.
Schelesinger, it may help you to review the definition of a half life. If you understand the implications of a half life you would understand why DNA would be found in other subjects far older then 521 years and you would understand essentially exactly how much DNA could be expected.
Or it just shows that in the moa DNA degrades after 521 years. That's only one species. Who know who it reacts in others? I know DNA is the same across species, but that doesn't mean it degrades at the same rate in all species. That's a rather limiting study. I think it's too early to say anything definitively.
This is nonsense. There's been dozens and dozens of reports of DNA isolated from sources orders of magnitude older than 521 years:
1) DNA sequence from Cretaceous period bone fragments. http://www.ncbi.nlm.nih.gov/pubmed/7973705
2) Amplification and sequencing of DNA from a 120-135-million-year-old weevil. http://www.ncbi.nlm.nih.gov/pubmed/8505978
3) Dozens more citations here: http://www.mhrc.net/ancientDNA.htm
It seems interesting. But are we sure that between 600 and 8,000 years old, the preservation conditions have not changed ? If during this period, there were strong climate oscillations with thawing-freezing of the bones, I guess that the DNA could be degraded faster.