The Punctuated Clock

David Hagerberg mik_daha at luecology.ecol.lu.sexx
Fri Jun 13 10:55:57 EST 1997


Richard M Kliman wrote:
> 
> In article <andrew.rambaut-ya023380001106971642160001 at news.ox.ac.uk>,
> Andrew Rambaut <andrew.rambaut at zoology.ox.ac.uk> wrote:
> >In article <01bc75df$d148d7a0$180819c4 at intekom2968>, "MEV V/D MERWE"
> ><vdmerwea at intekom.co.za> wrote:
> >
> >> 1. The fact that evolution takes place is not only relevant to us as
> >> humans, but to the whole of Ghaia, since it changes the essential make-up
> >> of all living organisms on earth. Molecular techniques has helped a great
> >> deal in defining evolution, but we have to see the big picture. Since a
> >> change in the DNA of an organism results in a change of its phenotype,
> >> natural forces interact with the phenotype and only indirectly with the
> >> genotype. Mutations thus occur not as a result of natural selection against
> >> the DNA of the organism, but against the traits that DNA codes for.
> 
> Independent of the Gaia argument, I think the term you want is
> "substitution."  That is, unless you are suggesting that mutations arise
> in response to selection, and I don't think that's what you mean.
> 
> >Many mutations in protein coding DNA do not result in a change in amino
> >acid due to the redundancy of code. Thus these occur despite natural
> >selection as there is no phenotype to be selected.
> 
> This is not always true.  There is considerable evidence for selection
> acting on silent substitutions, probably favoring those that increase the
> efficiency and/or fidelity of translation.

That means that they are not silent, since they have an effect. Though 
the Dawkinian gene concept does not cover an overall change off 
GC-content (for example), I think that it is to be considered as an 
active inheritable change. Though genes not expressed are to be 
considered silent and with no impact on fitness, as it has been shown.



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