Frequency/distribution of nucleotides/amino acids before selection

Donald Forsdyke forsdyke at post.queensu.ca
Mon Nov 2 11:34:52 EST 1998

Donal Hickey wrote:
> Here is another paper (from our lab) that shows a correlation between
> protein composition and nucleotide composition.
> =========================================
> ================================================
> Jean Lobry wrote in message <714r9s$pv7 at net.bio.net>...
> >On Wed, 21 Oct 1998 17:53:14, Dr.Ram Samudrala
> <ram.samudrala at stanford.nojunkemail>
> >wrote:
> >>
> >> Have there been any estimates published on the frequency/distribution
> >> of nucleotides/amino acids in DNA/protein sequences PRIOR to
> >> selection, i.e., before selection kicks in? I can get the frequencies
> >> of amino acids in known protein sequences, but these proteins have
> >> generally arisen through natural selection.
> >>

> >I'am not sure that this answers your question but in
> >  Lobry, J.R. (1997) Influence of genomic G+C content on average amino-acid
> >  composition of proteins from 59 bacterial species. Gene 205:309-316
> >
> >you find how to compute theoretical amino-acid frequencies as function of
> >nucleotidic frequencies in absence of selection. This is not difficult,
> >you just have to take care that there are no stop codons in coding
> sequences.
> >
> >Jean Lobry
      Drs. Hickey and Lobry have both accepted Dr. Samudrala's 
premise that base composition changes "before selection kicks in". 

How do we know when "selection" first "kicks in"? 

Sincerely, Donald Forsdyke
(see http://post.queensu.ca/~forsdyke/evolutio.htm).

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