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Author Topic:   Blood in dino bones
Mammuthus
Member (Idle past 6588 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 57 of 138 (195375)
03-30-2005 6:39 AM
Reply to: Message 3 by Minnemooseus
03-25-2005 12:02 AM


An illustration of failed expectations
The DNA potential for this sample are at present grossly overstated. If we look at much more recent sub fossils such as woolly mammoths, where biomolecules are preserved, the quality and quantity are substantially reduced when compared to any recent or near recent samples.
quote:
Science. 1980 Jul 11;209(4453):287-9. Related Articles, Links
Mammoth albumin.
Prager EM, Wilson AC, Lowenstein JM, Sarich VM.
Serum albumin was detected immunologically in muscle from a mammoth that died about 40,000 years ago. Rabbits injected with ground mammoth muscle produced antibodies that react strongly with elephant albumin, weakly with sea cow albumin, and still more weakly or not at all with other mammalian albumins. Since elephant albumin elicited antibodies with the same specificity, some of the surviving mammoth albumin molecules evidently have antigenic sites identical to those on native elephant albumin. Much of the mammoth albumin has, however, undergone postmortem change. The small amount of soluble albumin extractable from mammoth muscle is heterogeneous in size, charge, and antigenic properties.
In addition to the very low albumin content, a chemical analysis of the "well preserved" Dima mammoth demonstrated that almost all elements one would expect in an organic sample were only a tiny fraction of normal i.e. phosphorous in the sample was below 1% of normal.
A perhaps more appropriate comparison to the Dinosaur is illustrated by the DNA from amber debacle. In the early 90's multiple claims of insect DNA sequences were published. Yet when further scrutinized, none of the results were reproducible as shown in this paper
quote:
Austin JJ, Ross AJ, Smith AB, Fortey RA, Thomas RH. Problems of reproducibility--does geologically ancient DNA survive in amber-preserved insects?
Proc R Soc Lond B Biol Sci. 1997 Apr 22;264(1381):467-74.
or even possibly fraudulent.
quote:
Gutierrez G, Marin A.
The most ancient DNA recovered from an amber-preserved specimen may not be as ancient as it seems.
Mol Biol Evol. 1998 Jul;15(7):926-9.
One cannot rule out the possibilty of extremely well preserved samples. Even dinosaur. This says nothing about sample age but rather the preservation conditions. There are plenty of samples 100 years old that will not yield any DNA whereas frozen mammoth samples or even coprolites over 40 K yield abundant (albeit fragmented) DNA. Age and DNA preservation are not particularly well correlated.
I find it odd that Schweitzer and colleagues jumped to a discussion of DNA and preserved biomolecules rather than focusing on the morphological data that they DO have.

This message is a reply to:
 Message 3 by Minnemooseus, posted 03-25-2005 12:02 AM Minnemooseus has not replied

Replies to this message:
 Message 59 by simple, posted 03-31-2005 2:17 AM Mammuthus has replied

  
Mammuthus
Member (Idle past 6588 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 62 of 138 (195643)
03-31-2005 3:35 AM
Reply to: Message 59 by simple
03-31-2005 2:17 AM


Re: An illustration of failed expectations
Hi Simple,
Probably the best one could hope for even with successful extraction and characterization of dino DNA would be to place dino's in their relative phylogenetic position in relation to other vertebrates. Perhaps rates of sequence evolution estimates would gain another calibrator but from a single sample and species the value of this is kind of doubtful. More likely the group will stumble into contamination like the first report of dino DNA in the early 90's which was demonstrated to be a human sequence.
For a fairly easy to read summary of ancient DNA research (though it is a bit dated) you might want to check out the following article
Paabo S.
Ancient DNA.
Sci Am. 1993 Nov;269(5):86-92.
Cheers
M

This message is a reply to:
 Message 59 by simple, posted 03-31-2005 2:17 AM simple has not replied

  
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