A human, an octopus, and a coral may appear to have almost nothing in common, but their chromosomes still contain recognizable fragments inherited from an animal ancestor that lived more than 600 million years ago. Researchers at the University of Vienna have now traced how those ancient genomic pieces were reorganized as animal life diversified. The study, published in Science Advances, suggests that animal genomes do not evolve through an unlimited number of possible routes.
Instead, chromosome changes tend to move along a restricted set of irreversible pathways that the researchers describe as "evolutionary highways." The findings may also provide a valuable foundation for efforts to understand and conserve animal biodiversity. Tracing More Than 600 Million Years of Genome Evolution Every living animal ultimately descends from a common ancestor that existed more than 600 million years ago. Since that time, chromosomes have repeatedly fused, separated, and been rearranged as new animal lineages emerged.
Thousands of animal genomes have now been sequenced, but comparing their long-term evolution has remained difficult. In this study, an international team led by University of Vienna researchers brought thousands of genomes together in a single large-scale comparison. "Understanding these rules of evolution doesn't just tell us about the past," said Oleg Simakov, a professor at the University of Vienna who co-led the study.
"It also lets us ask where genome evolution might go next and enables us to identify key measures for the conservation of animal biodiversity." Many sequenced genomes remain "drafts." They can reveal which genes an animal possesses without showing exactly where those genes are positioned along its chromosomes. Chromosome-scale assemblies provide much more detail by arranging genes in their proper order across complete chromosomes. Producing these assemblies is considerably more difficult, and only recently have enough species been analyzed at this level to make a broad comparison across the animal kingdom possible.
Largest Chromosome Comparison Across the Animal Tree of Life The researchers examined more than 5,800 publicly available chromosome-scale genomes representing 4,454 species from 19 animal phyla. According to the team, this is the largest comparison of its kind across the animal tree of life. To organize such a vast amount of information, the scientists created a framework called evolutionary genome topology.
It places the enormous variety of animal genome structures onto a single map. That map revealed an important pattern. Genome architecture does not appear to change randomly.
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