From: Robert J. Bradbury (bradbury@www.aeiveos.com)
Date: Sat Oct 09 1999 - 05:21:49 MDT
On Sat, 9 Oct 1999, Damien Broderick wrote:
>
> Nor only that, human chromosome 2 is the fused remains of two different
> chromosomes in other primates. Would this matter, if the bulk of the same
> genetic data is still there in both cases? Dunno, but I wouldn't suggesting
> trying this experiment at home.
>
If the genetic material is the same, i.e. the fusion did not result
in putting the genes on one chromosome under the control of regulatory
regions on the other chromosome, then it shouldn't matter. Nature
appears to be pretty flexible in allowing chromosome # changes.
The problem with chromosome mergers is that you have a chromosome
with 2 centromeres which means that there is the possibility of
the chromosome getting ripped apart during cell division.
So one centromere has to be lost or "silenced" during the
fusion process. Similarly for chromosome division to occur
the chromosome without a centromere must somehow gain one.
[The centromeres are the regions of the duplicated chromosomes that
get "grabbed" to allow them to be separated during cell division.]
In the long run I think we will compress the genome onto 3-5
chromosomes: (1) A chromosome with all materials necessary for
basic cell biochemistry, metabolism & maintenance; (2) A chromosome
with all genes necessary for cell replication; (3) A chromosome
with "individuality" traits, especially the Major Histocompatibility
Complex; (4) A chromosome with the male/female/unisex traits;
(5) A chromosome with organ specific traits.
The are a number of advantages to this type of scheme. As you
develop, chromosome 5 gets edited so that the unused portions
of the chromosome in individual tissues get deleted (your liver
doesn't need your heart genes & your heart doesn't need your
liver genes). [Chromosome editing now occurs in the maturation
of the cells in your immune system, so this isn't that much
of a stretch.] When cells reach their final developmental
stage, those that no longer require division (neurons, muscle
cells, kidney cells, etc.) actually delete chromosome 2 because
a chromosome lacking the genes for cell division cannot become
cancerous. Chromosome 1 is engineered to have substantially
greater inherent DNA repair capacity and Chromosome 2 is
constructed with many redundant backup copies of genes
required for "checkpointing" cell division. Those 2 changes
should eliminate most cancer cases.
It is probably worth noting, that you should be able to construct
chromosome 1 or maybe 5 with a resistance to all known viruses
(by having them produce anti-sense RNA for the viral genes).
The above is why it seems silly to play with turning primates
into humans or humans into primates (unless you are doing it
simply as a means of self-entertainment).
Robert
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:05:27 MST