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.
Isn't this really the $64K question? In general, it's hard to find proteins _before_
selection has acted on them. I'm aware of a study (Hillis, in Science, maybe 1 yr
ago?) on nucleotide sequence changes over generations of bacteriophage growth.
I should think it would be difficult even to determine whether or not "selection" has
"acted" on a given stretch of genetic information. I contend (as a nucleic acid
biochemist, not an evolutionist) that since we don't know the function (or, all the
functions) of large stretches of DNA, or even of amino acids in well-characterized
proteins, we have no way of knowing whether amino acid or nucleotide changes are
fixed as a result of selection or not.
I would certainly appreciate informed comment on this topic!
o-----------------------------------------------------------------o
| Dr. Peter Gegenheimer | Vox:785-864-3939 FAX:785-864-5321 |
| Dept Molecular Biosciences | PGegen at UKans.edu |
| Dept Ecol & Evol Biology | http://RNAworld.Bio.UKans.edu/ |
| University of Kansas | |
| 2045 Haworth Hall | "The sleep of reason produces |
| Lawrence KS 66045-2106 | monsters." Goya |
o____________________________|____________________________________o
