Sequence differences between man and chimp genomes

Brian Fristensky frist at cc.UManitoba.CA
Mon Feb 9 13:46:22 EST 1998

Family Albrecht wrote:

> The chimp is the closest organism to man and there is a 99% homology in
> DNA sequences. What do we know about the other 1%? Surely this critical
> DNA should be the object of intensive analysis because it could lead us
> to the molecular essence of "humaness"? I believe technology exists for
> genome subtraction in the test tube, isolation, cloning and sequencing,
> so why cant I find any papers on the subject except that of Ueda et al
> (Genomics,8, 7-12, 1990 -"Human-specific sequences:Isolation of
> species-specific DNA regions by genome subtraction"). They claim to have
> isolated a sequence about 2000 bp long which is absent in the chimpanzee!
> What could this be? Current dogma has it that human DNA contains no new
> genes compared to the chimp-only small changes. Is this true? Any
> comments will be appreciated.
> Carl Albrecht

  These oft-cited hybridization results are greatly misleading.  For
example,  a few base changes in a protein sequence can drastically
change the specificity of a receptor or the Km or substrate specificity
of an enzyme. Equally important, small changes in regulatory proteins
or cis-acting regulatory sequence can have profound effects on
the expression of genes. Put another way, it's not just what
you have, it's what you do with it.

Another way to look at it is to consider how small aspects of software
can imact on what you can do. If you know Unix, think of all the
things that can be done  because of the ability of the operating system
to specify files or directories by symblic links. Or consider the subtlety
that can be added to a programming language by allowing recursion.

Perhaps the other side of the argument is to ask the question, why should
there be a lot of sequence difference between chimp and man? Sure
we can build Space Shuttles and MRI scanners, write poetry and
symphonies. These things may all be the result of a fairly small
number of subtle changes in how thinking works, from chimp
to man. I contend that the burden of proof lies on those who
support what I see as an outdated Man/animal dichotomy.  By most
ways of measuring, we're simply one step in a continuum.


Brian Fristensky                |
Department of Plant Science     |  "Computers are useless:
University of Manitoba          |   All they give you are answers."
Winnipeg, MB R3T 2N2  CANADA    |
frist at cc.umanitoba.ca           |  Pablo Picasso
Office phone:   204-474-6085    |
FAX:            204-474-7528    |

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