Posted by:
BGF
at Mon Nov 3 20:46:06 2003 [ Email Message ] [ Show All Posts by BGF ]
>>BGF wrote in another forum:
>>
>>"Actually, pax6 is part of the basic genetic toolbox and was actually expressed in the primitive eye. This is not a convergent evolution but rather the multiple use of an ancient tool (as opposed to a recent useless tool such as yourself)."
>>
>>Dr. Fernald of Stanford University writes:
>>
>>"It is well known that Pax-6 organizes other structures besides eyes and is even necessary for the onset of various actions outside the nervous system. Also, other genes can cause development of eyes [reviewed in 10]."
>>
>>Therefore it appears that BGF's info is outdated and/or inaccurate. There is no such thing as "the primitive eye" since eyes of different animal groups evolved independently of each other. The fact that they independently converged on the use of the same gene in most (but not all cases) is proof that convergent evolution of the same strategy is not only possible but probable.
Gee, you really don't have much of a grasp of evolution do you? As discussed very nicely in 'From DNA to diversity: molecular genetics and the evolution of animal design', Pax6 in the mouse and teh eyesless ortholog in Drosophila are both located at the top of the regulatory heirarchies that direct eye development in both. Other components of the pax6-regulatory circuit, including sine oculies, eyes absent and opsin genes, are also shared between flies and mice. In addition, pax6 orthologs are expressed during eye divelopment in other bilaterian phyla, providing even more evidence that the developmental functional similarities between mouse pax6 and Drosophila eyeless are not convergent. The remarkable conservation of pax6 expression and pax6-regulatory circuit suggests that all bilaterian eyes share a common developmental genetic circuit and that this circuit was present in the bilaterian ancestor.
> Hence if two or more snake lineages have converged on the same strategy of using the same chemical precursors as venom, then it is in perfect accord with known principles of evolution.
Ah yes but we are not relying on the simple presense of a particular toxin type but rather examined through rigorous phylogenetic analyeses and the results robustly supported a single origin of venom.
Ciao
B
-----
Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne
www.venomdoc.com
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RE: The Pax-6 gene and the evolution of venom - BGF, Mon Nov 3 20:46:06 2003