Indel

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An indel is a short polymorphism that corresponds to the addition or removal of a small number of bases in a DNA sequence. Indels are quite abundant, although not quite as abundant as SNPs. It is estimated that there are 1-2 million short indels segregating at low to high frequency in modern human populations. The vast majority of indels occur in short tandem repeats.

Example

A 2-base deletion

Reference         ACTGACACACACACTG
Variant1          ACTGACACACAC--TG

A 2-base insertion

Reference         ACTGACACACACAC--TG
Variant1          ACTGACACACACACACTG