There's a fair number of amino acids that have codons with two or even three differing bases. But you're right that that isn't most of them. And for most of them, the first codon nucelotide has to be the same.
But for most of them, the second and third can be changed. (Maybe you missed that some of them are listed twice?) I would offer that 2 out of 3 is large enough to be described as "probable."
Look at the figure Crash, where are you getting this stuff from?!!!
Apart from the stop codons a change in the 2nd base position is
always non-synonymous. Only Leucine and Arginine have 6 codons and can support changes at the 1st position. Given that third base wobble is not always effective, in many cases there are only 2 codons for a particular residue, we arrive at the figure I previously mentioned ~30% of substitutions will cause synonymous mutations. 30% is certainly a large enough probability to ensure frequent occurence, but certainly not enough to merit being described as the probable outcome.
Your quote from the Talk.Origins site suggests that 70-80% is the extreme range which
some proteins can tolerate rather than that most can, as you claim. Going by any normal system of referencing it seems likely that they cite no reference for this figure as the nine references are all from points 1, 2 and 4.
Nonetheless it's fairly clear that there is much resistance to mutation in the protein generation mechanism.
I wouldn't say resistance as such, but there is certainly a fairly high tolerance for mutations, contrary to what many creationists claim.
TTFN,
WK
This message has been edited by Wounded King, 10-27-2004 01:09 PM