Viviane Callier writes:

Chromosomes, the bundles of DNA that star in the mitotic ballet of cell division, play a leading role in complex life. But the question of how chromosomes came to exist and evolve has long been discouragingly hard to answer. This is due partly to the lack of chromosome-level genomic information and partly to the suspicion that eons of evolutionary change have washed away any clues about that ancient history.

Now, in a paper appearing today in Science Advances, an international team of researchers led by Daniel Rokhsar, a professor of biological sciences at the University of California, Berkeley, has tracked changes in chromosomes that occurred as much as 800 million years ago. They identified 29 big blocks of genes that remained recognizable as they passed into three of the earliest subdivisions of multicellular animal life. Using those blocks as markers, the scientists deduced how the chromosomes fused and recombined as those early groups of animals became distinct.

The researchers call this approach “genome tectonics.” In the same way that geologists use their understanding of plate tectonics to make sense of the appearance and movement of continents, these biologists are reconstructing how various genomic duplications, fusions and translocations created the chromosomes we see today.

The work heralds a new era in comparative genomics: Previously, researchers studied collections of genes from different lineages and described the changes one base pair at a time. Now, as more chromosome-level assemblies become available, researchers can trace the evolution of entire chromosomes back to their origin. They can then use that information to make statistical predictions and rigorously test hypotheses about how groups of organisms are related. [Continue reading…]