InsertionDeletion

Insertion–deletion mutations, commonly called indels, are genetic alterations in which bases are inserted into or deleted from a genome. Indels can range from a single nucleotide to large blocks of DNA and can affect any genomic region.

In coding sequences, the impact depends on the net change in length. Indels whose length is not a multiple of three often cause frameshift mutations, altering downstream amino acid sequences and frequently introducing premature stop codons. In coding and noncoding regions alike, indels can disrupt regulatory elements, splice sites, or RNA structure, potentially altering gene expression.

Indels arise through several molecular mechanisms, including errors during DNA replication (slippage), unequal crossing over during recombination, and repair of double-strand breaks. They are pervasive across organisms and contribute substantially to genetic diversity.

Detecting indels poses technical challenges, especially for small insertions/deletions in repetitive sequences. Modern methods combine short-read sequencing with specialized variant callers; long-read sequencing and complementary technologies improve detection of larger indels and complex rearrangements.

Biologically, indels influence evolution, population genetics, and disease. They can be neutral, deleterious, or occasionally advantageous, depending on their location and size. In humans, pathogenic indels underlie various genetic disorders, while in comparative genomics they serve as informative markers in phylogenetics and diversity studies.