Re: DNA at last

[NEIL CLARK <NCLARK@museum.gla.ac.uk>]

> I copied this out of the San Jose Mercury News this morning.
> 
> US TEAM EXTRACTS FRAGMENTS OF DNA FROM DINOSAUR 
BONES

>    Paleontologist Jack Horner, and advisor on Steven Spielburg's hit 
film
> about dinosaurs, managed to isolate fragments of DNA from the 
femur of a
> Tyrannosaurus Rex, the Sunday Times reported.(me: what Sunday 
times?  The London Sunday Times?)

Yes

Betty sent this in.  I guess that my earlier email did not transmit.  I 
copied the original from the Sunday Times and made a few comments 
on it.

The method used is PCR (polymerase chain reaction).  This method is 
prone to contamination.  I have heard of one case where an organism 
being studied in an adjacent lab was able to contaminate a sample.  
The sample was contaminated anyway by being touched, being in 
contact with airborne organisms, and having been taphonomically 
altered by bacteria.  Basically, the PCR "amplifies" fragments of DNA 
so that they can be identified.  The problem is that the contaminents 
are also "amplified" or multiplied, and it is virtually, if not wholly, 
impossible to distinguish what is a fragment of dino-DNA and 
contaminent DNA.

I took part in a course on taxonomy at Glasgow recently where PCR 
was covered.  The conclusion was that the results obtained for fossil 
material over 10,000 years old are unreliable.


Neil Clark
Curator of Palaeontology
Hunterian Museum
University of Glasgow
email: NCLARK@museum.gla.ac.uk

The first law of Geology is the law of supposition.
(Geological Howlers - ed. WDI Rolfe)