For example, the work shows that humans are more closely related to rodents than to dogs or cats.
The team, which includes Jeff Touchman -- an assistant professor of biology at Arizona State and director of the sequencing facility at the Translational Genomics Research Institute, Phoenix -- published its findings in the Aug. 14 issue of Nature.
The report, "Comparative analyses of multi-species sequences from targeted genomic regions," details the comparison of one targeted region of the human genome (a segment of the human chromosome 7, which includes the gene mutated in cystic fibrosis) to the same region of other vertebrates ranging from chimpanzees to zebrafish. Touchman directed the sequencing effort of this work while he was at the National Institutes of Health, Bethesda, Md.
"This is a significant genomic achievement," Touchman said. "We can learn a lot about the human genome by comparing it to the genomes of other species."
The team, which included 71 researchers from 10 institutions, made the comparisons of the human genome to that of the chimpanzee, baboon, cat, dog, cow, pig, rat, mouse, chicken, two species of puffer fish (fugu and tetraodon) and zebrafish.
Touchman said the work is both a technical achievement in the amount of the genome sequenced (1.8 million base pairs in each of the 12 species), as well as for what will be learned by comparing these genome sequences together. It could provide clues as to how each vertebrate evolved.
"One of the things we examined was how much of the genome sequence was 'conserved' across organisms," Touchman said.
As organisms evolved into species, specific sequences were conserved, or selected for retention in the genome, over millions of years of evolution. The sequences that were conserved are thought to be strong candidates for being biologically significant to the survival of that species.
"We already know that genes are very highly conserved across vertebrate species, but what we are finding now is that not only are genes conserved, but other anonymous sequences are conserved as well," Touchman said. "These regions are likely to control important functions such as gene expression."
Also, by studying the differences in the genome of humans compared to other vertebrates, the researchers could determine when organisms split off and headed in different evolutionary directions. For example, the work shows that genetically humans are more closely related to mice and rats than to dogs and cats.
"This has been a controversial issue," Touchman said. "We determined this by looking at the ancestral repetitive sequences that are in these genomes and compared them to each other to infer phylogenic relationships."
Touchman added that the real significance of the work might lie in the paradigm of comparing large regions of genomic sequence together, from multiple species to explore functional similarities and differences in the genetic code of those species. Because sequencing is an arduous and costly task, scientists do not have complete sequences of the genomes of many species. But they are eager to begin the comparative study of genomes.
"The work provides a first glimpse of the type of genomic studies that will occur in the future as more and more whole genomes are sequenced," Touchman said.
For a copy of the paper, go to: www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v424/n6950/full/nature01858_fs.html
Source:
Jeff Touchman, jtouchman@tgen.org
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