Author Affiliation: Department of Genetics and Neurology, University of North Carolina, Chapel Hill.
One of the most important insights of the genomics revolution is that basically all mammals have roughly the same number of genes and a given gene usually has an obvious homolog in other species. Changes in proteins' amino acid sequence and differences in the developmental pattern of gene expression determine why we look and behave differently from other mammals. The genes adjacent to a given gene in humans are often the same in mammals to which we are evolutionarily the most closely related and less so in more distantly related species. Characteristically, genomes of different mammals are rearranged such that blocks of synteny (blocks of homologous genes that are in the same order) seem randomly shuffled and sometimes duplicated as they are distributed across chromosomes. This shuffling of the location of bits of the genome, which changes the local environment of genes, likely has an effect on the developmental pattern of gene expression that occurred across millennia of evolution. It should not be surprising that we can see evidence of this same type of rearrangement occurring in the human population if we look closely. In the last 2 decades, a revolution in our understanding of the human genome has taken place in large part by the desire to understand the etiology of human diseases, which reveals the evolutionary forces at work on our genomes.
Wilhelmsen KC. Significance of Genomic Rearrangements in Epilepsy. Arch Neurol. 2012;69(3):305-307. doi:10.1001/archneurol.2011.3256