Stephan J. Sanders, Christopher E. Mason, in Genomics, Circuits, and Pathways in Clinical Neuropsychiatry, 2016. Insertions and Deletions. Insertions and deletions (indels) are when DNA is lost (deletion) or gained (insertion) on a smaller scale, defined as <1000 bp (Fig. 1.4D).If the indel occurs within a coding region, it is described as being “in-frame” if the amount of DNA lost or ...