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Reciprocating Bill

Posts: 4265
Joined: Oct. 2006

(Permalink) Posted: Dec. 30 2008,09:38   

Daniel is referring to (and somewhat misrepresenting) these findings:
The compact genome shows remarkable complexity, including conserved gene content, gene structure and synteny relative to human and other eumetazoan genomes. Despite the absence of any known developmental program and only a modest number of cell types, the Trichoplax genome encodes a rich array of transcription factors and signalling genes that are typically associated with embryogenesis and cell fate specification in eumetazoans, as well as other genes that are consistent with cryptic patterning of cells, unobserved life history stages and/or complex execution of biological processes such as fission and embryonic development in these enigmatic creatures....

Although the Trichoplax body plan is simple, its genome encodes a rich array of transcription factors and signalling pathways that are typically associated with eumetazoan developmental patterning and cell-type specification. A question remains: what role do these genes have in placozoans? Cellular morphology may be deceptive, and complex gene expression patterns may define functionally distinct but morphologically cryptic cellular subtypes. This would be consistent with models in which transcription factors associated with gene expression patterns for specific differentiated cell functions in the eumetazoan ancestor were co-opted in cnidarians and bilaterians for patterning roles. We speculate that signalling and transcription factor genes may be involved in complex regulatory events required for the known processes of growth, fission and/or swarming, or the as yet undescribed processes of sexual reproduction and embryonic development.

So the first response to the question of the function served by these genes is "We don't know."

The second response is to hypothesize unobserved cellular and behavioral differentiation coded by these genes, differentiation that, in a related lineage that was ancestral to the eumetazoans (including ourselves), were exapted (co-opted) for patterning roles in the building of more complex animal bodies. If so, the animal is quite "in place."

Daniel, you'll notice that this hypothesis generates testable predictions, e.g. the existence of functionally distinct but morphologically cryptic cellular subtypes, a role for these genes in complex known and unknown regulatory, behavioral, sexual and embryological activities, and so on. This is the stuff evolutionary biology thrives on.

Myth: Something that never was true, and always will be.

"The truth will set you free. But not until it is finished with you."
- David Foster Wallace

"Here’s a clue. Snarky banalities are not a substitute for saying something intelligent. Write that down."
- Barry Arrington

  19624 replies since Jan. 17 2006,08:38 < Next Oldest | Next Newest >  

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