From: Mitchell Porter (mitch@thehub.com.au)
Date: Sun Jan 12 1997 - 18:11:54 MST
[Tony Csoka]
> I mean, the same chemicals that composed the "primordial soup" from which
> life arose on this planet, and perhaps elsewhere, would probably still be
> around today whether life arose or not. WHAT "SELECTIVE ADVANTAGE" IS THERE
> FOR THE CHEMICALS TO FORM INCREASINGLY COMPLEX PATTERNS?
The reason why the genome _can_ become more complex would just be that
DNA is a polymer, and can get longer and longer. Probably there's an
upper limit to the length of a single chromosome, but you can add new
chromosomes. Mechanisms of length-increase probably involve insertion
or retention of multiple copies of DNA; e.g. extra copies of chromosomes
are made at replication, or perhaps mRNA is spliced back into the genome
somewhere by reverse transcriptase.
One reason bigger genomes could be advantageous: by allowing for more
adaptable organisms. The more useful add-ons an organism has, the more
adaptable it is liable to be, but each add-on will require extra genes.
A ceiling on genome length is probably a ceiling on adaptability (until
brains get into the picture).
-mitch
http://www.thehub.com.au/~mitch
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