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molecular clocks

Tom Holroyd tomh at BAMBI.CCS.FAU.EDU
Fri Sep 6 21:12:08 EST 1991

>From: bashford at scripps.edu (Don &)

>The question of the validity of the molecular clock is different from
>the question of evolutionary bursts.  Since a large proportion of DNA
>bases are probably "silent" (i.e. mutations are neutral), it is
>possible that genotype variation displays a meaningful and constant
>rate while phenotype variation (if one had a measure of it) would
>display bursts and have no meaningful rate.

OK, I see the point now.  The thing is, can you ever observe
constant genotypic variation?  Wouldn't speciation events cause
unpredictable changes in the observed rate?  Hmm.  Maybe not, because
the line that survives would continue to accumulate mutations
at the same rate it had before the speciation event.

I still wonder about totally neutral mutations.  What would be an example?
How do we know a large proportion of bases are silent?

Tom Holroyd
Center for Complex Systems
Florida Atlantic University
tomh at bambi.ccs.fau.edu

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