Stephen cited King and Wilson (1975) as a relevant authority, and
in the quoted material there was discussed these techniques:
Immune reactions
Electrophoresis
Protein sequences
Annealing techniques
The first three techniques are based upon small-scale
sampling, which Stephen cites as a difficulty. DNA
hybridization, though, is based upon large-scale sampling,
involving much longer stretches of DNA than are referenced by
any of the other techniques. DNA hybridization provides a
comparison without reference to whether the sequence being
analyzed is composed of coding regions, non-coding regions,
or a mixture of the two.
WRE>The number of genes/loci comes from genomic
WRE>sequencing studies. Stephen is invited to explain why anyone
WRE>would expect the number of loci found via genomic sequencing
WRE>to alter our opinion of the confidence with which to hold the
WRE>DNA hybridization result.
SJ>I already said "why". "If humans have The have *twice* as many
SJ>genes (140,000) as previously thought (60,000-80,000)" and
SJ>"unless of course chimps turn out to have twice as many genes
SJ>as first thought too", then the statement that `humans share
SJ>98% of their genes with chimps' will be wrong. Humans and
SJ>chimps might share 98% of their *known* genes, but that does
SJ>not necessarily mean that they share 98% of their total genes.
That's why I clarified my response to address the similarity of
DNA, not genes.
SJ>The problem with the assumption that humans share 98% of their
SJ>genes was that: a) it was based on only a limited number of
SJ>proteins and fragments of DNA; b) those fragments of human DNA
SJ>that did not closely match that of chimps were discarded; and
SJ>c) as King and Wilson pointed out, their study only compared
SJ>structural genes. There might be major differences in
SJ>regulatory genes:
A genetic distance found by DNA hybridization is not subject to
the same criticisms as the small-scale smapling methods that
Stephen argues against above.
I'll restore the remainder of my discussion of DNA
hybridization as a measure of genetic similarity.
Of course, skeptics can point to the position of Dr. Marks on
the original DNA hybridization work. See
<http://socrates.berkeley.edu/~jonmarks/biblio.html>. But
even Marks' table would not increase the difference more than
another 1.7 percent or so. Marks criticizes the claim that
DNA hybridization is capable of resolving the three-way split
between humans, chimpanzees, and gorillas. Marks does not
appear to argue that there are huge differences between humans
and chimpanzees. I would welcome correction on my
characterization of Marks' stance from anyone who has the
relevant papers.
Even the anti-evolutionary page at
<http://www.pblcoc.org/rr/r%26r9609a.htm> manages to
recognize and discuss the differences in approach.
A basic description of DNA hybridization can be found at
<http://www.science.lander.edu/rsfox/111syst.html>.
Another link:
<http://www.enconnect.net/rjtolle/ART14.htm>.
I find it interesting that the small-scale and large-scale
genetic similarity measures all lead to such nicely congruent
results.
Wesley