Structural variant

Sub-microscopic structural variation

Sub-microscopic structural variants are much harder to detect owing to their small size. The first study in 2004 that used DNA microarrays could detect tens of genetic loci that exhibited copy number variation, deletions and duplications, greater than 100 kilobases in the human genome. However, by 2015 whole genome sequencing studies could detect around 5,000 of structural variants as small as 100 base pairs encompassing approximately 20 megabases in each individual genome. These structural variants include deletions, tandem duplications, inversions, mobile element insertions. The mutation rate is also much higher than microscopic structural variants, estimated by two studies at 16% and 20% respectively, both of which are probably underestimates due to the challenges of accurately detecting structural variants. 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.