Re: dinosaur cloning

["Ralph Miller III" <gbabcock@best.com>]

Chandler Gibbons MGibb21521@aol.com writes:
> Would it be possible to clone a dinosaur by using Loh's method?  That is,
> grinding up large quantities of dinosaur bone to get SOME of the DNA
sequence,
> then fill in the gaps with avian, reptilian, or amphibian DNA?

No.  Even if you could retrieve DNA from Cretaceous fossils (which is
uncertain at this time, as DNA probably is degraded and altered over time),
how could you make sense of fragments of DNA without a blueprint?  How
would you know what order to put the DNA material into?  How would you know
what was missing?  How would you know what DNA from extant animals could be
used to replace the unknown components?  The use of frog DNA in _Jurassic
Park_ seems especially foolish, as frogs are so derived (evolved) from a
tetrapod ancestor of dinosaurs.  Crocs and birds at least are archosaurs,
but what pieces of which species would be required to fill in which blanks
in the sequence for which species of dinosaur?  An individual animal's
genetic information is very complex, with about a billion properly ordered
bases, which must be arranged on the correct number of chromosomes, and
with the correct proteins present, and most of the genetic material of a
modern plant or animal is just so much ancestral baggage, not visibly
expressed in an individual's physical body.  The genes must be turned "on"
or "off" as required, stimulated by the proper hormones.  Good luck!
   
  Would it be
> possible to use the method explained in Jurassic Park, where they take
ancient
> DNA from a blood-sucking insect incased in amber?

Would that it were so simple.  (In other words, no).  You cannot simply
take a hypodermic needle and extract the DNA nor even the liquid blood from
the body of a blood-sucking insect in amber.  Whereas the amber fossils are
very unusual in preserving the actual original body of an animal without
any permineralization (without replacing the body with rock), the resulting
preserved remains are dried up, something like an Egyptian mummy.  The best
one could do to get blood material from the abdomen of such a specimen
would be to spritz the interior with a liquid, swish it around, and then
remove the liquid.  The result would not be the same as fresh blood, and so
far as I know no one has succeeded in retrieving any dinosaur DNA in this
manner.  DNA was reportedly extracted from the wing muscle of a Cretaceous
bee in an amber fossil, but other scientists were unable to replicate
(repeat) the success of the original experiment, so the results of the
initial experiment have been challenged.  There are many problems, not the
least of which is the potential for contamination.

  What other means could one
> get dinosaur DNA?  Is there any?

Mary Higby Schweitzer has studied what may be organic material in the blood
vessel channel within the bone marrow inside the bones of _Tyrannosaurus
rex_, as well as the feather-like fibers on _Mononychus_ (or is it
_Shuvuuia_?).  While I am not aware of complete genomes being retrieved
from these specimens ;^), Schweitzer's preliminary work suggests the
possibility that some original proteins may survive to this day. 
Schweitzer does not expect to revive extinct dinosaurs, but she hopes that
her studies may some day help us to better understand the phylogenetic
relationships between dinosaurs and other animals.  This research may also
give us insight into the evolution of beaks, feathers, and so forth.

Schweitzer's paper, _Molecular Paleontology: Rationale and Techniques for
the Study of Ancient Biomolocules_, from Farlow and Brett-Surman's _The
Complete Dinosaur_ covers the above subject (and also provides a host of
references for further study).  There is a book, which I believe is called
_The Science of Jurassic Park_, that also covers this subject in some
detail.  Nova had an enjoyable program entitled "The Real Jurassic Park"
which ran through the logistical problems of producing and maintaining a
population of dinosaurs.  In this program, Robert Bakker proffers a
different science fiction scenario for bringing back the dinosaurs: turning
on and off the genes of living birds (referring to the experiment which
produced tooth enamel in a modern bird).  It would take a serious
Frankenstein/Dr. Moreau to pull it off, but who knows?

Also, there are apparently scientists hoping to recover sperm from frozen
mammoths for insertion into the eggs of modern elephants in order to
produce hybrids which could over many years of selective breeding produce a
living mammoth.

I should point out, of course, that most paleontologists do not expect to
see living dinosaurs any time soon, excepting the avian ones (birds) and
those two dimensional impostors which show up in movies from time to time
(as in _JP_).
 
-- Ralph Miller III     gbabcock@best.com