> From: mcdonald at wsuhub.uc.twsu.edu> Subject: Re: Evolutionary tree of *all* proteins
...
> evolution by sequence convergence. It is quite possible
> that, for some important cellular functions, there are
> a few protein motifs that outperform all others. Therefore,
> there may be strong selection among some proteins to
> develop such a motif. The point is that, in this scenario,
> we have proteins becoming more similar in sequence due to
> selection over time (i.e., convergent evolution).
...
> comparative genetic maps, etc.). Otherwise, I think sequence
> difference gives a good estimate of evolutionary distance
> but does not necessarily reveal the direction of evolution
> (i.e., are the proteins headed their seperate ways or are
> they on a collision course?).
Ah, but DO protein sequences ever converge? I know a lot of people
have said they do, but at least one rather authoratative figure has
recently said that they do NOT - at least, not in such a way as to
obscure their phylogenies (Doolittle RF, (1994). Convergent
evolution: the need to be explicit. Trends in Biochemical Sciences
19: 15-18).
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