Indel is a molecular biology term for an insertion or deletion of bases in the genome of an organism. It is classified among small genetic variations, measuring from 1 to 10 000 base pairs in length, including insertion and deletion events that may be separated by many years, and may not be related to each other in any way. A microindel is defined as an indel that results in a net change of 1 to 50 nucleotides.
In coding regions of the genome, unless the length of an indel is a multiple of 3, it will produce a frameshift mutation. For example, a common microindel which results in a frameshift causes Bloom syndrome in the Jewish or Japanese population. Indels can be contrasted with a point mutation. An indel inserts and deletes nucleotides from a sequence, while a point mutation is a form of substitution that replaces one of the nucleotides without changing the overall number in the DNA. Indels can also be contrasted with Tandem Base Mutations (TBM), which may result from fundamentally different mechanisms. A TBM is defined as a substitution at adjacent nucleotides (primarily substitutions at two adjacent nucleotides, but substitutions at three adjacent nucleotides have been observed).
Indels, being either insertions, or deletions, can be used as genetic markers in natural populations, especially in phylogenetic studies. It has been shown that genomic regions with multiple indels can also be used for species-identification procedures.
An indel change of a single base pair in the coding part of an mRNA results in a frameshift during mRNA translation that could lead to an inappropriate (premature) stop codon in a different frame. Indels that are not multiples of 3 are particularly uncommon in coding regions but relatively common in non-coding regions. There are approximately 192-280 frameshifting indels in each person. Indels are likely to represent between 16% and 25% of all sequence polymorphisms in humans. In fact, in most known genomes, including humans, indel frequency tends to be markedly lower than that of single nucleotide polymorphisms (SNP), except near highly repetitive regions, including homopolymers and microsatellites.
The term "indel" has been co-opted in recent years by genome scientists for use in the sense described above. This is a change from its original use and meaning, which arose from systematics. In systematics, researchers could find differences between sequences, such as from two different species. But it was impossible to infer if one species lost the sequence or the other species gained it. For example, species A has a run of 4 G nucleotides at a locus and species B has 5 G's at the same locus. If the mode of selection is unknown, one can not tell if species A lost one G (a "deletion" event") or species B gained one G (an "insertion" event). When one cannot infer the phylogenetic direction of the sequence change, the sequence change event is referred to as an "indel".
- Mills, R. E. (9 August 2006). "An initial map of insertion and deletion (INDEL) variation in the human genome". Genome Research. 16 (9): 1182–1190. doi:10.1101/gr.4565806. PMC 1557762. PMID 16902084.
- Mullaney, J. M.; Mills, R. E.; Pittard, W. S.; Devine, S. E. (21 September 2010). "Small insertions and deletions (INDELs) in human genomes". Human Molecular Genetics. 19 (R2): R131–R136. doi:10.1093/hmg/ddq400. PMC 2953750. PMID 20858594.
- Kondrashov AS, Rogozin IB (February 2004). "Context of deletions and insertions in human coding sequences". Hum. Mutat. 23 (2): 177–85. doi:10.1002/humu.10312. PMID 14722921.
- Ogurtsov AY, Sunyaev S, Kondrashov AS (August 2004). "Indel-based evolutionary distance and mouse-human divergence". Genome Res. 14 (8): 1610–6. doi:10.1101/gr.2450504. PMC 509270. PMID 15289479.
- William M. Gelbart; Lewontin, Richard C.; Griffiths, Anthony J. F.; Miller, Jeffrey H. (2002). Modern genetic analysis: integrating genes and genomes. New York: W.H. Freeman and CO. pp. 736. ISBN 0-7167-4382-5.
- Gregory TR (January 2004). "Insertion-deletion biases and the evolution of genome size". Gene. 324: 15–34. doi:10.1016/j.gene.2003.09.030. PMID 14693368.
- Halangoda A, Still JG, Hill KA, Sommer SS (2001). "Spontaneous microdeletions and microinsertions in a transgenic mouse mutation detection system: analysis of age, tissue, and sequence specificity". Environ. Mol. Mutagen. 37 (4): 311–23. doi:10.1002/em.1038. PMID 11424181.
- Sachin apurwa; Wilson MD; Rubio JM; Post RJ (March 2004). "A molecular marker for the identification of Simulium squamosum (Diptera: Simuliidae)". Ann Trop Med Parasitol. 98 (2): 197–208. doi:10.1179/000349804225003118. PMID 15035730.
- Gonzalez KD, Hill KA, Li K, et al. (January 2007). "Somatic microindels: analysis in mouse soma and comparison with the human germline". Hum. Mutat. 28 (1): 69–80. doi:10.1002/humu.20416. PMID 16977595.
- Kaneko T, Tahara S, Matsuo M (May 1996). "Non-linear accumulation of 8-hydroxy-2'-deoxyguanosine, a marker of oxidized DNA damage, during aging". Mutat. Res. 316 (5–6): 277–85. doi:10.1016/S0921-8734(96)90010-7. PMID 8649461.
- Hill KA, Wang J, Farwell KD, Sommer SS (January 2003). "Spontaneous tandem-base mutations (TBM) show dramatic tissue, age, pattern and spectrum specificity". Mutat. Res. 534 (1–2): 173–86. doi:10.1016/S1383-5718(02)00277-2. PMID 12504766.
- Buettner VL, Hill KA, Halangoda A, Sommer SS (1999). "Tandem-based mutations occur in mouse liver and adipose tissue preferentially as G:C to T:A transversions and accumulate with age". Environ Mol Mutagen. 33 (4): 320–324. doi:10.1002/(SICI)1098-2280(1999)33:4<320::AID-EM9>3.0.CO;2-S. PMID 10398380.
- Väli U, Brandström M, Johansson M, Ellegren H (2008). "Insertion-deletion polymorphisms (indels) as genetic markers in natural populations". BMC Genetics. 9: 8. doi:10.1186/1471-2156-9-8. PMC 2266919. PMID 18211670.
- Erixon P, Oxelman B (2008). Volff J (ed.). "Whole-gene positive selection, elevated synonymous substitution rates, duplication, and indel evolution of the chloroplast clpP1 gene". PLOS ONE. 3 (1): e1386. Bibcode:2008PLoSO...3.1386E. doi:10.1371/journal.pone.0001386. PMC 2148103. PMID 18167545.
- Pereira, F.; Carneiro, J.; Matthiesen, R.; van Asch, B.; Pinto, N.; Gusmao, L.; Amorim, A. (4 October 2010). "Identification of species by multiplex analysis of variable-length sequences". Nucleic Acids Research. 38 (22): e203. doi:10.1093/nar/gkq865. PMC 3001097. PMID 20923781.
- Nakamura, H; Muro, T; Imamura, S; Yuasa, I (March 2009). "Forensic species identification based on size variation of mitochondrial DNA hypervariable regions". International Journal of Legal Medicine. 123 (2): 177–84. doi:10.1007/s00414-008-0306-7. PMID 19052767.
- Taberlet, P.; Coissac, E.; Pompanon, F.; Gielly, L.; Miquel, C.; Valentini, A.; Vermat, T.; Corthier, G.; Brochmann, C.; Willerslev, E. (26 January 2007). "Power and limitations of the chloroplast trnL (UAA) intron for plant DNA barcoding". Nucleic Acids Research. 35 (3): e14. doi:10.1093/nar/gkl938. PMC 1807943. PMID 17169982.
- Hui Bai, Yinghao Cao, Jianzhang Quan, Li Dong, Zhiyong Li, Yanbin Zhu, Lihuang Zhu, Zhiping Dong (2013). "Identifying the Genome-Wide Sequence Variations and Developing New Molecular Markers for Genetics Research by Re-Sequencing a Landrace Cultivar of Foxtail Millet". PLOS ONE. 8 (9): e73514. Bibcode:2013PLoSO...873514B. doi:10.1371/journal.pone.0073514. PMC 3769310. PMID 24039970.CS1 maint: multiple names: authors list (link)
- Zheng, L. Y., Guo, X. S., He, B., Sun, L. J., Peng, Y., Dong, S. S., ... & Jing, H. C. (2011). "Genome-wide patterns of genetic variation in sweet and grain sorghum (Sorghum bicolor)". Genome Biology. 12 (11): R114. doi:10.1186/gb-2011-12-11-r114. PMC 3334600. PMID 22104744.CS1 maint: multiple names: authors list (link)
- 1000 Genomes Project, Consortium; Durbin, RM; Abecasis, GR; Altshuler, DL; Auton, A; Brooks, LD; Durbin, RM; Gibbs, RA; Hurles, ME; McVean, GA (2010-10-28). "A map of human genome variation from population-scale sequencing". Nature. 467 (7319): 1061–73. Bibcode:2010Natur.467.1061T. doi:10.1038/nature09534. PMC 3042601. PMID 20981092.