On 24/11/2006, at 12:05 PM, Alberto Vieira Ferreira Monteiro wrote:
I am pretty much familiar with Down Syndrome [my oldest daughter
has it].
I didn't know that (or didn't recall it). So you understand the
principle. There is a plethora of similar conditions depending on
which chromosome is duplicated or deleted. Some interesting sex
chromosome ones like Turner's, and so on.
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?
Sorry, I don't know much about the specific differences, I just know
a bit about this particular thing as it's a really good piece of
human evolution information.
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.
Not really, development is far more robust than that and it somehow
seems to sort itself out a lot more than you'd think. You can chop an
awful lot of DNA about before causing real problems. It's sort of
like the fragmentation of a really full really old pair of FAT drives
- it just keeps muddling along and if one allele doesn't work the
other is read. Gene duplication is common, and is a major driving
force in variation (as if you duplicate a vital gene, changes can
occur to one copy without affecting the other).
That's not to say there aren't problems, as you're well aware, but it
isn't as easy to break as one would think (just look at chimeras!)
Charlie
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