> Mike Waller wrote:
>
> > Maybe we could expand the equipment to identify DNA from bird fecal samples
> > as well.

On Tue, 20 Jun 1995, Burton Guttman wrote:

> Sorry, Mike. The DNA you'll recover from fecal samples will be the DNA of
> the animal's gut bacteria and the phage that grow in them. (And maybe
> from sloughed gut epithelium, but it will all be mixed together.) I guess
> it could be used to identify where an animal came from if you had some
> animal poop, but it won't tell you anything about ivory or gall bladder,
> and it won't answer any speciation questions--except maybe about
> speciation in the bacteria and viruses.

Not necessarily so!

Yes, you would expect to have all sorts of DNA other than the stuff you
want in feces, but certain techniques would allow you to extract the stuff
you want from the "contaminants." For example, polymerase chain reaction
(PCR) "amplifies" fragments of DNA. That is to say, it finds a fragment
and makes copies of it. Lots of copies, since the doubling time is only
minutes, and the cycle can be repeated indefinitely (hence "chain
reaction"). For this discussion, the important point is that PCR
amplifies *specific* stretches of DNA. Even *species-specific* stretches.
So you can selectively amplify your bird's DNA from it's poop, using PCR,
because the PCR reaction will ignore the bacterial and viral DNA, and
copy only, e.g. owl DNA from owl poop. If the owl has been eating other
owls, then you're in trouble, though ;)

It takes a lot of work, which I skipped in the above description
(basically, you have to know a lot about the DNA fragment you want to
amplify, and that takes work to figure out). It's not easy or
cheap. But it certainly should be _possible_.

Chris Hill
Seattle, WA
cehill at u.washington.edu