
Researchers tracked changes in chromosomes that occurred as much as 800 ma BP. They identified 29 big blocks of genes that remained recognizable as they passed into 3 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.” 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. But what would cause blocks of genes to stay linked together? 1 explanation for this phenomenon, which is called synteny, relates to gene function. It may be more efficient for genes that work together to also be physically located together; that way, when a cell needs to transcribe genes, it doesn’t have to coordinate transcription from multiple locations on different chromosomes. Unless a chromosome rearrangement conveys a big functional advantage, it’s inherently hard for the rearrangement to spread. And rearrangements are typically not advantageous: During meiosis and the formation of gametes, all chromosomes need to pair up with a matching partner. Without a partner, an odd-sized chromosome won’t become part of a viable gamete, so it is unlikely to make it into the next generation. Small mutations that reshuffle the gene order within chromosomes can still occur.


