 It has also been shown that the generation of spontaneous structural variants significantly increases the likelihood of generating further spontaneous single nucleotide variants or indels within 100 kilobases of the structural variation event.Copy-number variation (CNV) is a large category of structural variation, which includes insertions, deletions and duplications.In recent studies, copy-number variations are tested on people who do not have genetic diseases, using methods that are used for quantitative SNP genotyping.