How long does DNA last.

[Micaiah]

DNA breaks down after a certain period of time. Getting a handle on the time taken for this to occur would give some indication of the age of certain fossils.

How long does it take for DNA to break down, and what are the implications of this on the dating of fossils?

 

[sulphur]

Why would you use DNA for the dating of fossils?

 

[Micaiah]

Just another check perhaps. Am I correct in saying they do find DNA from fossils?

 

[sulphur]

Not for dating purposes or perhaps you can show me an example from the last two weeks

 

[RufusAtticus]

Nuclear DNA breaks down quickly. Mitchondrial DNA can survive as long as 100,000 years or so.

There are no implications for dating fossils since fossils are not dated using DNA. When PCR first came out, there were papers published claiming to have amplified DNA from dinosaurs or other long extinct creatures. However, these were not repeatable and in many instances close scrutinity of the sequences revealed modern origins, i.e. contamination, which agreed with what chemists had been saying about the stability of DNA.

 

[JohnR7]

Originally posted by Micaiah
Just another check perhaps. Am I correct in saying they do find DNA from fossils?

Is this a set up for another debate? There is no clock in the DNA, that is as accurate as the atomic clock. So of course supporters of evolution say the DNA is evidence of evolution and life that lived millions of years ago.

Young Earth Creationists believe the DNA supports their position that the earth and all that is in it is only thousands of years old.

http://www.grisda.org/origins/22081.htm

 

[Micaiah]

Nuclear DNA breaks down quickly. Mitchondrial DNA can survive as long as 100,000 years or so.

That confirms what I read somewhere. If we can agree on this time frame, then suppose they find a fossil and give it an age of 3 million years, and the DNA can still be recognised, then there is clearly something wrong with the dating. Are there cases where this has happened?

 

[sulphur]

There are far more reliable methods beinng used now. Why use DNA. please give me a valid scientific explanation

 

[Micaiah]

I think you're missing the point here Sulphur. I'm not suggesting that DNA be used as a method of dating, but simply that there is something strange dating a fossil as being 'x' million years old when DNA can still be recognised. It could prove a useful sanity check on dating.

 

[sulphur]

Sorry could make alittle more sense please

 

[Late_Cretaceous]

I remember reading about researches who claimed to have imaged the chromosomes from dinosaur fossils.  This may be the case, however, it does not mean that the DNA was intact - just that the shape of the chromosomes was preserved.

 

[sulphur]

Which has nothing to do with dating

 

[Micaiah]

Is this the usual claim that is made regarding DNA in fossils that are 'x' million years old.

 

[RufusAtticus]

Originally posted by Micaiah
That confirms what I read somewhere. If we can agree on this time frame, then suppose they find a fossil and give it an age of 3 million years, and the DNA can still be recognised, then there is clearly something wrong with the dating. Are there cases where this has happened?

That is a big if. The cases where DNA has been "recovered" from fossils over the 100,000 years old are inconclusive because they couldn't be repeated. Many of the studies have been shown to be "recovering" technician or bacteria DNA, not the DNA from the organism the fossil represents.

 

[RufusAtticus]

Originally posted by JohnR7
http://www.grisda.org/origins/22081.htm

Ohh, a 1995 article, which in the area of Ancient DNA is extremely out dated. The amber studies have been dismissed, some probably even before 1995, because the DNA did not come from the fossil organisms.

"These troublesome fossils contain DNA in concentrations that should be expected only in specimens less than 10,000 years old; yet they have been assigned ages that extend beyond 125 million years."

This is a great example of the problem: recovering DNA is not the same as recovering DNA from a 125 million year old object.

 

[Micaiah]

Isn't this the kind off stuff science fiction is made of. You take a dinosaur DNA and using clone technology, presto, you get a living dinosaur.

Would you agree though that if they did recover real DNA from an assumed 'x' million year old fossil, then it would cast doubt on the original aging of the fossil?

 

[RufusAtticus]

Originally posted by Micaiah
Would you agree though that if they did recover real DNA from an assumed 'x' million year old fossil, then it would cast doubt on the original aging of the fossil?

I'm not sure what you're asking here. These studies always recover real DNA, it's just from a source they hadn't planned on.

Now if a study finds DNA from a "million-year" old sample, and is able to rule out modern contamination, then, yes, it would suggest that the geological dating of the sample should be checked. However, the geological dating could turn out to be accurate, and the DNA lasted so long because the fossil was preserved under "special" conditions.

 

[lucaspa]

Originally posted by Micaiah
DNA breaks down after a certain period of time. Getting a handle on the time taken for this to occur would give some indication of the age of certain fossils.

How long does it take for DNA to break down, and what are the implications of this on the dating of fossils?

It depends on the  method of preservation.  All polymers can be broken under the right chemical or enzymatic conditions.  After death of the organisms the lysosomes break, releasing their degredative enzymes, including proteases to break down the histones and DNAses to cleave DNA.  Also, extremes of pH will cleave the phosphodiester bonds connecting one nucleotide to another.  Also, decay bacteria will introduce their own enzymes.

Now, how long does it take for all the DNA to be reduced to trinucleotides or less? Depends.  Insects stuck in amber could take millions of years.  Osteocytes in their lacunae of bone are impervious to bacteria. If the chemical activity is such that the bone is not being replaced, the osteocytes could remain intact for millions of years.  (Whether there are enough of them to get enough DNA for analysis is another story, of course.) 

Mostly, mtDNA has been used not because it survives longer but because it is the only DNA that can track changes on a relatively short time scale.  That is what it is mtDNA used in studying neandertals.

But some DNA has been recovered from dino bones that are over 80 million years old.

Sorry, but this isn't going to serve as your criteria to dispute dating or evolution.

 

[lucaspa]

Originally posted by Micaiah
Would you agree though that if they did recover real DNA from an assumed 'x' million year old fossil, then it would cast doubt on the original aging of the fossil?

No.  Because breakdown of DNA is so dependent on the preservation process. In conditions of pH around 7 and no lysosomal or bacterial enzymes to degrade it, DNA can last nearly indefinitely.

 

[JohnR7]

Originally posted by Micaiah
Isn't this the kind off stuff science fiction is made of. You take a dinosaur DNA and using clone technology, presto, you get a living dinosaur. 

Not really "presto", you could not use the origional DNA if it is that old. You would have to use it as a pattern to make your own DNA and then maybe you can made a dinosaur out of that.

But only if you can get Laura Dern & Jeff Goldblum to star in it.