peter.unmack at ASU.Edu wrote:
> On Sat, 25 Apr 1998, Bruce Hansen wrote:
>
> > 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