insertionsdeletions

Insertions and deletions, collectively known as indels, are types of genetic mutations in which one or more nucleotides are inserted into or deleted from a genome relative to a reference sequence.

Indels vary from single-nucleotide changes to large segments spanning thousands of bases. When an insertion or deletion occurs within a gene’s coding region, it can alter the reading frame. If the indel length is not a multiple of three, it typically causes a frameshift that changes downstream amino acids and often introduces a premature stop codon. Indels in noncoding regions can affect gene regulation, splicing, or chromatin structure.

Indels arise through several cellular processes, including replication slippage, unequal crossing over during meiosis, poor double-strand break repair, and activity of transposable elements. Repetitive sequences are particularly prone to indel formation and to sequencing or alignment errors.

Detection of indels relies on DNA sequencing and read alignment to a reference genome. Indel calling can be challenging in repetitive regions; specialized tools and realignment steps are used. Validation may involve targeted sequencing or orthogonal methods.

Biological effects of indels range from benign to severely deleterious. Frameshift indels often disrupt protein function, while in regulatory regions they can modify expression levels or splicing. Some indels can be beneficial and contribute to adaptation in populations.

In humans and other organisms, indels are common sources of genetic variation and disease-associated mutations. Somatic indels are frequently observed in cancer genomes and can drive tumor development.