Re: Mutated brain gene: part of what makes us human


"Guy A Hoelzer" <hoelzer@xxxxxxx> wrote in message
news:f24qov$s1l$1@xxxxxxxxxxxxxxxxxxxxxx
This is a very interesting statistic, although I don't
really know what to
make of it yet. I want to point out, however, that this
protein difference
number is not at all comparable to the DNA sequence
difference number,
because the former represents amino acid strings while the
later represents
individual nucleotides. For example, I'm sure that every
human chromosome
(strings of nucleotides) has a different sequence than
their homologous
chimp chromosomes. Does this mean that their DNA is 100%
different? This
is the same logic that underpins the claim that 80% of the
proteins are
different. Some would consider it impressive that 20% of
the proteins are
identical along complete amino acid sequences. I would
like to see the
comparison of amino acid identity between humans and
chimps to compare with
the 99% nucleotide identity estimate between the same two
species. Amino
acid identities may be greater than 99%, despite having a
difference of 80%
at the whole protein level.

Guy


in article f229fh$2g7d$1@xxxxxxxxxxxxxxxxxxx, DK at
dk@xxxxxxxxxxxxxxxxxxxxxxxxx wrote on 5/11/07 10:34 AM:

In article <f20bkd$1860$1@xxxxxxxxxxxxxxxxxxx>,
dk@xxxxxxxxxxxxxxxxxxxxxxxxx
(DK) wrote:
In article <f1t1qn$2cnf$1@xxxxxxxxxxxxxxxxxxx>, Tim
Tyler
<seemysig@xxxxxxxxxxxxxx> wrote:
"Gene mutation linked to cognition is found only in
humans"

- http://www.physorg.com/news97825267.html

OK, so humans have an additional splice isoform. Big
deal.
Unless I missed something, there are many such
examples.
Certainly a far cry from "part of what makes us human"
(unless you wanted to say "one part out of few
thousands").

That "human and chimpanzee genomes vary by just 1.2
percent"
thing is getting old and overused anyway. Truth is,
when one
looks at identity at protein/ORF level, humans and
chimps only
have 80% identity. Or, to put it the other way, one out
of five
proteins is different.

Actually, I was writing it from memory and my memory got
it all backwards. In fact, chimps and humans share only
20%
of *identical* proteins. The rest 80% are ever slighly
but different.
Not to imply that every one contributes to phenotypic
differnces
but, clearly, possibilities are endless. Here is the
original paper:


http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15716
009

Eighty percent of proteins are different between humans
and chimpanzees
Galina Glazko, Vamsi Veeramachaneni, Masatoshi Nei, and
Wojciech Makayowski

So, to edit it corectly:

Considering that a single mutation in a single protein
can
drastically alter the way an entire cell or a whole
organism
behave, the 80% difference looks appropriately very
significant
and that "humans and chimps are 99% identical" - quite
stupid.

DK

Yeah--all the talk of DNA and protein equivalence mean very
little I think when the true pertinent
factor[s?] of interest is brain comparability (due to macro-
and micro-structure/organization/etc.) with respect to, say,
"self-consciousness" (SC) or simply, "thinking."

In Douglas Hofstadter's new book, "I Am a Strange Loop," he
takes on the theoretical basis for SC and thus its synonyms,
"thinking," "soul," etc., though only in his opinion
however. His personal
subjective scale of SC for typical things from rocks and
tomatoes to insects, rodents etc. and humans (in arbitrary
units of "Hunekers" [sp], humans arbitrarily avg. of 100)
makes one wonder if any meaningful talk of organic chemistry
wrt this subject is really worth while at all.

BTW, at least the first half of the book is as brilliant as
"Godel, Escher, Bach" was, but it does
become somewhat overly verbose and repetitive by the end.
Still, a worthwhile read I think* if one often asks oneself
the question, "what is SC?" He is indeed a great thinker and
good writer!

*Since it pretty much agrees with everything I have said in
NGs in the past about SC's nature. :)
.....tonyC


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