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jeannot



Posts: 1200
Joined: Jan. 2006

(Permalink) Posted: Dec. 07 2011,14:32   

Quote (Tracy P. Hamilton @ Dec. 06 2011,19:04)
 
Quote (Cubist @ Dec. 06 2011,18:20)
   
Quote (Southstar @ Dec. 06 2011,12:54)

Hi,

I've been looking for some example of gain-of-function mutation that has derived from speciation.

That seems backwards to me. Mutations, including gain-of-function mutations in specific, are the stuff of which speciation is made, not so? Wouldn't it be more reasonable to ask for examples of speciation derived from gain-of-function mutation, rather than the other way around?

Most speciation is not driven by natural selection, but by accumulation of genetic differences.

This dichotomy is false. A genetic difference involved in reproductive isolation can be promoted by selection. In fact, that has been show to be the case for most genes causing reproductive isolation (and that's for species pairs where hybrid deficiency isn't environment-dependent. For the others, the contribution of natural selection to speciation makes no doubt).
On the other hand, there is very little evidence for speciation by genetic drift.

Regarding the issue of "gain-of-function derived from speciation", I'm not sure what that means. Speciation is not  the motor of genetic novelty, it's an outcome. (EDIT: as Cubist said).

It's also unclear what "gain-of-function" means. In ecological speciation, an ecological trait diversifies, which enhances reproductive isolation. For instance, feeding on seeds of a different sizes. Is that a new function?
Speciation takes place between populations that are initially similar, and species don't grow new organs often.
Sure there might be physiological/biochemical functions that may bot be externally visible. Whether they contribute to reproductive isolation is hard to tell. The genes causing reproductive isolation remain largely uncovered (they're identified in a handful of species).

Here's an example of what may be qualified as gain of function: http://www.pnas.org/content....38.long
An aphid species has acquired some venom as a result of the duplication of a protease gene. I'm not sure this has anything to do with speciation though, and this may not be testable.
There's the famous example of Heliconius butterflies that mimmic other butterfly species. Wing patterns are also involved in reproductive isolation (a case of ecological speciation). Would a new pattern (e.g. red stripes, derived from a uniform color) be considered as a gain-of function?

  
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