progenitor gene

Andrew J. Roger roger at evol5.mbl.edu
Fri Jun 20 06:45:50 EST 1997


I screwed up my little figure. Please excuse it. The one below
might be better...but might not.


Andrew J. Roger wrote:
> 
> Susan Hogarth wrote:
> >
> > higginss at VAX.CS.HSCSYR.EDU wrote:
> > >
> > >... Also, what extant
> > > organism is considered the most ancient.
> >
> > Could you explain what this means? On the surface, the question seems to
> > be "What is the oldest thing still living?", but I suspect you mean
> > something different...
> 
> I suppose it could mean: what living organism displays the most
> retained ancestral features of the latest common ancestor of
> all life?  I think this could be a reasonable question.  My
> bet is that eubacteria, in general, probably are most similar
> to the latest common ancestor of life in their overall cellular
> architecture-- they prokaryotic cells with ester-linked fatty-acyl
> lipids, with a circular chromosome and genes organised into
> operons. It seems that the cenancestor (most recent common
> ancestor) probably had all of these features if one accepts
> the following tree:
>                      			Ester/Fatty-acyl  	Circ chromo   	Operons
>      _____ Eubacteria     	YES					YES          	YES
>     /
> ---/   ___ Archaebacteria  	NO           		YES    			YES
>    \ 
>     \/
>      \
>       \___ Eukaryotes      	YES     			NO          	NO
> 
> Of course the overall similarity of an organism to an ancestor will
> depend on what characters you choose to evaluate AND how you weight
> the various characters.
> 
> Cheers
> Andrew J. Roger



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