Mapping and sequencing of structural variation from eight human genomes

Genetic variation among individual humans occurs on many different scales, ranging from gross alterations in the human karyotype to single nucleotide changes. Here we explore variation on an intermediate scale—particularly insertions, deletions and inversions affecting from a few thousand to a few million base pairs. We employed a clone-based method to interrogate this intermediate structural variation in eight individuals of diverse geographic ancestry. Our analysis provides a comprehensive overview of the normal pattern of structural variation present in these genomes, refining the location of 1,695 structural variants. We find that 50% were seen in more than one individual and that nearly half lay outside regions of the genome previously described as structurally variant. We discover 525 new insertion sequences that are not present in the human reference genome and show that many of these are variable in copy number between individuals. Complete sequencing of 261 structural variants reveals considerable locus complexity and provides insights into the different mutational processes that have shaped the human genome. These data provide the first high-resolution sequence map of human structural variation—a standard for genotyping platforms and a prelude to future individual genome sequencing projects. Pieces of eight genomes Clone-based sequencing of the genomes of eight unrelated individuals — four African and four non-African — has been used to build a picture of human genetic variation. The study concentrated on intermediate-scale variations a few thousand to a few million base pairs long. The results confirm the finding that African genomes are more diverse than other groups, and suggest that previous estimates of the incidence of 'copy-number variant' base pairs have been too high. The data suggest that, despite recent evidence to the contrary, non-allelic homologous recombination is the dominant process in promoting structural variation in the genome. Studies of this type provide benchmarks for the many genome sequences that will be generated by next-generation technologies. This paper examines eight individual genomes using a clone-based sequencing approach, for structural variants of 8,000 nucleotides or more. One of the first high-quality inversion maps for the human genome is generated, and it is demonstrated that previous estimates of variation of this sort have been too high.