Re: Cool science: lancelets and 4Xing vertebrate genome
- From: Ron O <rokimoto@xxxxxxx>
- Date: Thu, 19 Jun 2008 04:45:22 -0700 (PDT)
On Jun 18, 4:28 pm, Glend <interelectromagne...@xxxxxxxxx> wrote:
"The late geneticist Susumu Ohno argued in 1970 that gene duplication
was the most important force in the evolution of higher organisms, and
Ohno's theory was the basis for original estimates that the human
genome must contain up to 100,000 distinct genes.
"Instead, the Human Genome Project found that humans today have only
20,000 to 25,000 genes, which means that, if our ancestors' primitive
genome doubled and redoubled, most of the duplicate copies of genes
must have been lost. An analysis of the lancelet, or amphioxus,
genome, being published in the June 19 issue of Nature, shows this to
be the case.
" "Amphioxus and humans had a common ancestor 550 million years ago,
which allows us to use amphioxus as a surrogate for that ancestor in
terms of understanding how vertebrate genomes evolved," said Daniel S.
Rokhsar, a faculty member in the University of California, Berkeley's
Center for Integrative Genomics and program head for computational
genomics at the Department of Energy Joint Genome Institute (JGI) in
Walnut Creek, Calif. Rokhsar and JGI post-doctoral fellow Nicholas H.
Putnam performed the sequencing, assembly and genome-wide analyses of
the amphioxus genome and are lead authors of the Nature paper.
" "If you compare the 23 chromosomes of humans with the 19 chromosomes
of amphioxus, you find that both genomes can be expressed in terms of
17 ancestral pieces. So, we can say with some confidence that 550
million years ago, the common ancestor of amphioxus and humans had 17
chromosomal elements." "
For well over a decade the researchers have been uncovering data
indicating that the common ancestor of all vertebrates was a
tetraploid that had doubled some ancestral genome. All the genomes
that are being sequenced is just confirming that. Since the genes are
redundant you can expect that there will be gene loss just through
deletion and drift over the half billion years that vertebrates have
been evolving. The real neat thing is when you find that some of the
duplicated genes are doing other things for the organisms. They have
gone on to do different things. Gene duplication and divergence is
one of the prime mechanisms for evolving new functional units, and we
now have multiple genomes of evidence that it happens.
Beats me why the "science" minded ID perps would object to this
conclusion or the evidence for it.;-)
Now they know part of the mechanism that their designer used to create
the vertebrate lineage. They should be over joyed to have something
to work with.;-)
Ron Okimoto
SNIP:
.
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