Structural variation, including copy number variants (CNVs, such as insertions and deletions) and copy neutral variation (such as inversions and translocations), may account for some of the unexplained heritability if those variants contribute to the genetic basis of human disease and are incompletely assessed by commercial SNP genotyping arrays. Although this type of variation has not been explicitly examined in most GWAS until now, CNVs in particular (regions 1 kilobase (kb) or longer present in variable numbers across individuals) have gained attention as methods to detect them have improved52,53. Other forms of structural variation such as inversions, translocations, microsatellite repeat expansions, insertions of new sequence, and complex rearrangements have been implicated in rare Mendelian conditions. For the most part such variation has been largely unexplored in relation to complex traits54.
