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Re: primers



On Wednesday 01 Dec 2004 21:30, Jeff Hecht wrote:
> At 7:58 AM +1100 12/2/04, Dann Pigdon wrote:
> >I think the real question was; if dogs were only known from fossil
> >remains, and DNA (nor interbreeding evidence) wasn't available,
> > would their range of variation still lend then to be recognised as
> > a single species? Or would the fact that skeletal structure is only
> > a tiny part of the variation of a species (and can be altered by
> > relatively minor genetic changes) mean that cladistics would
> > produce an over-simplistic view of relationships?
>
> The authors of the recent Science paper on the decline of bison
> populations found in their genetic studies that the plains bison and
> woods bison are genetically indistinguishable, although
> morphologically distinct, so this question has broader impact than
> the artificial diversity created by dog breeders. For the bison, I
> was told that some of the morphological distinction may have arisen
> from response to the local environment (e.g, thickness of coats).
>
But they tested only a small fraction of the mitochondrial DNA. Physical 
characteristics are determined by somatic genes. Though mitochondrial 
DNA is supposed to mutate faster than somatic DNA, there is a lot more 
somatic DNA, so the overall number of mutations over a given time may 
be more for somatic DNA. Therefore, a somatic mutation causing a change 
in physical characteristic, often used for species determination, may 
not be detected by testing mitochondrial DNA.

-- 

Gautam Majumdar

Please send e-mails to gmajumdar@freeuk.com