Charlie Bell wrote: > > Not so much. What's being discovered over the last decade or so is > that the system is prone to some pretty spectacular errors, but the > ways in which it can still produce a viable and often fertile > organism. In about 1/900 people, for example, a chromosomal fusion > occurs that actually changes the total chromosome number (a > Robertsonian translocation), and while some forms of this result in > an abnormality like trisomy 21 (Down's syndrome), if there's no > deletion or duplication of material, then the individual may suffer > no adverse symptoms. > I am pretty much familiar with Down Syndrome [my oldest daughter has it].
> In fact, it is precisely one of these translocations that provides > clear evidence for the chimpanzee/human relationship, where our > chromosome 2 is a fusion of material that is 2 chromosomes in chimps > (there's even the remnants of a centromere in there...). > That's interesting. Is this the biggest difference between human and chimp DNA? > So I doubt that the fertility issue is a serious one, and even > decreased fertility in F1 of a "mixed marriage" would probably be > compensated for by hybrid vigour in supsequent generations. > My point was that the "huge" number of duplications or n-plications of genes would turn the chromossomes into a mess. AFAIK, just one duplicated gene in the middle of it would make things complicated. Alberto Monteiro _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
