Editing Human genome (section)

=== Structural variation ===
Structural variation refers to genetic variants that affect larger segments of the human genome, as opposed to point [[mutation]]s. Often, structural variants (SVs) are defined as variants of 50 base pairs (bp) or greater, such as deletions, duplications, insertions, inversions and other rearrangements. About 90% of structural variants are noncoding deletions but most individuals have more than a thousand such deletions; the size of deletions ranges from dozens of base pairs to tens of thousands of bp.<ref name=":2">{{cite journal | vauthors = Abel HJ, Larson DE, Regier AA, Chiang C, Das I, Kanchi KL, Layer RM, Neale BM, Salerno WJ, Reeves C, Buyske S, Matise TC, Muzny DM, Zody MC, Lander ES, Dutcher SK, Stitziel NO, Hall IM | title = Mapping and characterization of structural variation in 17,795 human genomes | journal = Nature | volume = 583 | issue = 7814 | pages = 83–89 | date = July 2020 | pmid = 32460305 | pmc = 7547914 | doi = 10.1038/s41586-020-2371-0 | bibcode = 2020Natur.583...83A }}</ref> On average, individuals carry ~3 rare structural variants that alter coding regions, e.g. delete [[exon]]s. About 2% of individuals carry ultra-rare megabase-scale structural variants, especially rearrangements. That is, millions of base pairs may be inverted within a chromosome; ultra-rare means that they are only found in individuals or their family members and thus have arisen very recently.<ref name=":2" />