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From: kliman@mbcl.rutgers.edu
Newsgroups: sci.bio
Subject: Re: Coelocanth and evolution: Human chr. differences
Message-ID: <475.285665cf@mbcl.rutgers.edu>
Date: 12 Jun 91 22:19:59 GMT
References: <676362297.46@egsgate.FidoNet.Org> <1991Jun12.033532.3222@menudo.uh.edu>
Lines: 20

In article <1991Jun12.033532.3222@menudo.uh.edu>, davison@menudo.uh.edu (Dan Davison) writes:
> In article <676362297.46@egsgate.FidoNet.Org> Vincent.A.Mazzarella@f98.n250.z1.FidoNet.Org (Vincent A Mazzarella) writes:
> 
>    But, of course, genomes of every human is quite different from every other
>    human. What matters are those differences causing a change in phenotype.
> 
> Waitaminnithere.  "Quite?" Less than < 1% is quite?  Please define
> what you mean.  The chimp-human sequence divergence is about 1%, which
> I can't see a "quite different" by any stretch of the imagination. 

From a genetic standpoint, it seems to me that 1% sequence divergence is quite
substantial.  That would supply, on average, 1 change for every 33 codons.  Of
course, many of those changes would be silent (or effectively neutral, given
the similarity of many amino acids coded for by similar codons).  However,
some amino acid substitutions can have major phenotypic effects.  If we use
50,000 as the number of genes in humans (Science 252:1255), and figure that most
will differ in amino acid sequence when compared to those of chimps, we 
shouldn't be surprised by the degree of phenotypic divergence observed.

 - Rich Kliman