Human subtelomeres are hot spots of interchromosomal recombination and segmental duplication

Human subtelomeres are polymorphic patchworks of interchromosomal segmental duplications at the ends of chromosomes. Here we provide evidence that these patchworks arose recently through repeated translocations between chromosome ends. We assess the relative contribution of the principal mechanisms of ectopic DNA repair to the formation of subtelomeric duplications and find that non-homologous end-joining predominates. Once subtelomeric duplications arise, they are prone to homology-based sequence transfers as shown by the incongruent phylogenetic relationships of neighbouring sections. Interchromosomal recombination of subtelomeres is a potent force for recent change. Cytogenetic and sequence analyses reveal that pieces of the subtelomeric patchwork have changed location and copy number with unprecedented frequency during primate evolution. Half of the known subtelomeric sequence has formed recently, through human-specific sequence transfers and duplications. Subtelomeric dynamics result in a gene duplication rate significantly higher than the genome average and could have both advantageous and pathological consequences in human biology. More generally, our analyses suggest an evolutionary cycle between segmental polymorphisms and genome rearrangements. The chimpanzee genome The cover photo by Kevin Langergraber shows the adult female chimpanzee ‘Jolie’ in Kibale National Park, Uganda. This was taken on 16 August 2004, a few weeks before Jolie gave birth to her first infant. This week marks a landmark in the study of our closest living relative: the publication by the Chimpanzee Sequencing and Analysis Consortium of the initial sequence of the chimpanzee genome, together with a comparison with the human genome. The paper describes changes that have shaped human and chimpanzee species since the split from our common ancestor, and hints at what makes us uniquely human: 35 million single-nucleotide substitutions, 5 million small insertions and deletions, local rearrangements and a chromosome fusion. A comparison of gene duplications in chimpanzee and human genomes reveals gene expression differences that may underlie disease susceptibility. A study of primate genomes shows that subtelomeres are hot spots of recent chromosomal duplication and gene conversion. Conservation of Y-linked genes during human evolution is revealed by comparative sequencing in the chimpanzee. The final research paper in this collection fills a big gap in our knowledge: the first chim