To: All Msg #119, May2893 08:43AM Subject: How to Clone a Dinosaur Jim Hutchins raises a p
From: L.A. Moran
To: All Msg #119, May-28-93 08:43AM
Subject: How to Clone a Dinosaur
Organization: UTCC Public Access
From: firstname.lastname@example.org (L.A. Moran)
Jim Hutchins raises a point about whether it is possible to regenerate an
extinct organism from its DNA (as in Jurassic Park). Some of you might recall
that we had this discussion several years ago before Jurassic Park was
published. At that time someone claimed to be writing a book about cloning
dinosaurs from fossil DNA and sought our opinions about the possibility.
Jim Hutchins writes,
"What hasn't been stated clearly enough (yet) is that while the DNA
may be available, there's nothing you can do with it if you were
to get it.
I liked the book as much as the next biologist, but let's face it
folks, IT CAN'T BE DONE. Period. End of sentence."
Basically, Crichton and a crew of credulous molecular biologists
have completely forgotten that the epigenetic factors contained
within the oocyte are just as important as the DNA. This harks
back to Gunther Stent's classic _gedanken_ experiment: if we sent
the DNA code for a cat, and instructions for decoding it, to a
distant civilization who had never seen a cat, could they make one?
I think not, but will listen to any arguments others have.
Another way of putting it: 65 M years of evolution separate modern
lizards from the dinosaurs, just like the same amount of time
separates me from a lemur or a tree squirrel. Could you inject
_my_ DNA into the x-irradiated oocyte of a modern lemur, and get
a clone of me?"
I agree with you that knowing the sequence of DNA will not enable you to
reconstruct the organism. To his credit Crichton seems to be aware of this
problem and that is why the DNA is injected into modern eggs.
Your claim of impossibility relies on your belief that the evolutionary
distance between extinct dinosaurs and modern organisms is too great to
trigger proper development. I think that you are probably right when it
comes to fossil DNA from the Jurassic (about 180 million years ago). However,
it is well to keep in mind that organisms such as frogs and mammals and fruit
flys are also separated by distances as great as this and that some genes
can be successfully transferred between these species. There may be enough
homology between modern transcription factor recognition sites and those
sites in dinosaur DNA to get some expression.
If not, then in theory one could try replacing lizard (or whatever) DNA with
fossil DNA until one got an oocyte that could make a dinosaur. (Maybe it
would be better to "add on" dinosaur DNA rather than "replace" lizard DNA.)
Another way of overcoming this limitation would be to move backwards in time
by smaller increments. For example, we might be able to reproduce extinct
organisms from 20 million years ago and then use these to clone organisms
from 40 million years ago etc. If dinosaurs are our goal then we have to
start with those living species that are most closely related to dinosaurs
and follow that line. We may even have to go back beyond 200 milion years
ago and then forward along a line leading to raptors (we do want to clone
raptors, don't we?).
However, the real reason why this is impossible has nothing to do with the
question Jim raised. The real reason why it is impossible to create dinosaurs
from fossil DNA is that the newly hatched dinosaurs would collapse and die
as soon as they were born. You have forgotten that dinosaurs could not support
their own weight on our modern world. We would have to move the Earth to the
vicinity of Saturn in order for the experiment to work because dinosaurs have
to be suspended between Earth and Saturn in order to stand up. Credibility
also has to be suspended. (-:
Laurence A. Moran
E-Mail Fredric L. Rice / The Skeptic Tank