> I like Mach's observation that perhaps we can use the DNA separation of
> morphologically similar "species" to help us define a group to examine more
> closely for physical differences.
Like most times you are all full of shit except Cary. :-) Although you are
correct in this specific statement too Bruce, although some times the
physical differences just aren't easy to find or simply virtually don't
exist (cryptic speciation). Mach was kinda right too in some of his
points. To clarify things a bit though, PCR has nothing to do with DNA
directly, it is simply used to amplify pieces of DNA. Take a look at
http://heg-school.awl.com/bc/companion/cmr2e/Activity/PCR/PCR01.htm if you
want more info on it. While all DNA has the same structure, not all DNA
is alike. Very basically you have two "types", coding and non-coding.
Coding regions contain genes, non-coding regions don't appear to do
anything, (though it is not really well understood from any perspective)
and is often called junk DNA. Junk DNA, because it doesn't code for
anything has a much higher apparent mutation rate, hence differences
between populations can evolve much faster. This makes it excellent for
population studies looking at variation within species. It is not
typically used for seperating species. To complicate matters more there
are several structures in cells that contain DNA, each having it's own
characteristics and peculiarities. Deping upon what question one is
asking depends upon which DNA they examine. Arguably the most commonly
used is mtDNA (mitochondrial DNA) as it is maternally inherited (you only
get your mother's copy) meaning it does not experience recombination.
This makes it excellent for studying the history of populations and
species (mostly for phylogenetic reconstruction). It is also good for
seperating species. There are many other variations on this theme that I
won't go into.
The main thing to remember is the technique depends upon the question
being asked and that the more different techniques one uses in the study
the more reliable the outcome will be relative to reality (including both
genetic and morphological techniques).
Tootles
Peter Unmack