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