how to test your dinosaur bones for DNA

[rowe@lepomis.psych.upenn.edu (Mickey Rowe)]

Since everybody seems to be putting out references, I guess I'll throw
in a couple more from the May 10th issue of _Science_:

Service, R. F. (1996). "Just How Old is that DNA, Anyway?", _Science_,
     272:810.

Poinar, H. N., Hoss, M., Bada, J. L., and Paabo, S. (1996). "Amino
     Acid Racemization and the Preservation of Ancient DNA",
     _Science_, 272:864-866.

The first is just a brief description of the second.  I'll be even
briefer: it appears that we're unlikely to get interpretable DNA
directly from dinosaur bones.  Amber is a much better source probably
because it keeps water away from the DNA and thus preserves it.  To
the extent that ancient DNA can be found anywhere, though, the second
article describes a cross-check.  The rate at which amino acids (in
proteins) racemize (convert from one form to that form's mirror image)
is the same as the rate of DNA degradation under a variety of
conditions.  Because of that, you can measure the degree of
racemization of a sample's amino acids and then infer whether or not
any associated DNA is likely to have survived intact.  Some samples
(e.g. the one described by Woodward of BYU -- the sample from the coal
mine in Utah -- and the _T. rex_ bones from Montana) have highly
racemized proteins indicating that the DNA they contained most likely
won't tell us much of anything about the DNA those samples contained
when the animals were alive.  The DNA from the 17 million year old
leaves from Moscow, Idaho are similarly suspect.

Somehow I expect to hear from Chip Pretzman on this one...

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)