The Punctuated Clock

Andrew Rambaut andrew.rambaut at zoology.ox.ac.uk
Fri Jun 13 06:45:43 EST 1997


In article <5nmp30$ooh at ruacad.runet.edu>, rkliman at runet.edu (Richard M
Kliman) wrote:

> >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.

The fact that many substitutions do not result in AA changes IS true. Some
of these may be select for or against due to tendancies related to G/C bias
etc. However it seems reasonably to say that most will simply be neutral -
i.e. they had no affect on phenotype and were fixed by drift. Indeed is
seems likely that many AA replacement substitutions will also be between
AAs that have a minimal effect on the protein structure (i.e. changes tend
to be withing AA groupings with respect to size and hydrophobicity).

Andrew

======================================================================
  Andrew Rambaut,             EMAIL - Andrew.Rambaut at zoology.ox.ac.uk
  Zoology Department,           WWW - http://evolve.zoo.ox.ac.uk/
  University of Oxford,         TEL - +44 1865 271272
  South Parks Road, Oxford, UK  FAX - +44 1865 271249
======================================================================
======================================================================
  Andrew Rambaut,             EMAIL - Andrew.Rambaut at zoology.ox.ac.uk
  Zoology Department,           WWW - http://evolve.zoo.ox.ac.uk/
  University of Oxford,         TEL - +44 1865 271272
  South Parks Road, Oxford, UK  FAX - +44 1865 271249
======================================================================



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