Genome sequence of lancelet shows how genes quadrupled during vertebrate...(ngdom and Spain reconstructed what happe...),Health

Date:6/18/2008

ngdom, and Spain, reconstructed what happened next. Each of those 17 ancestral segments was duplicated twice in the evolution of vertebrates, after which most of the routine "housekeeping" genes lost the extra copies. Those left, totaling a couple thousand genes, found new functions that, Putnam said, make us different from all other creatures.

"These few thousand genes have been retooled to make humans more elaborate than their simpler ancestors. They are involved in setting up the body plan of an animal and differentiating different parts of the animal," he said. "The hypothesis, pretty strongly supported by this data, is that the multiplication of this particular kind of gene and differentiation into different functions was important in the formation of vertebrates as we know them."

"The most exciting thing that the amphioxus genome does is provide excellent evidence for the idea that Ono proposed in 1970, that the human genome had undergone two rounds of whole-genome duplication with subsequent losses," said coauthor Linda Z. Holland, an expert on the biology and genetics of amphioxus at the Scripps Institution of Oceanography at UC San Diego who led the community effort to sequence and annotate the genome. "We have been kicking that idea around with very little proof for a long time. This genome sequence really clinches that."

Interestingly, the sea squirt Ciona intestinalis, a tunicate, was previously thought to belong to the the earliest chordate lineage because of the sea squirt's very simple body plan. Comparison of the lancelet, sea squirt and human genomes, however, show instead that the lancelet lineage diverged before the tunicates and vertebrates.

"Sea squirts and their relatives have taken the basic chordate genome and simplified it in various ways, while amphioxus retains those features in its genome," said Rokhsar.

The researchers are trying to reconstruct what happened at the end of the Cambrian period 5
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Contact: Robert Sanders rsanders@berkeley.edu 510-643-6998 University of California - Berkeley Source:Eurekalert

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