Insertions

Insertions are a type of translocation, and indeed they are sometimes referred to as “insertional translocation,” “interstitial translocation,” or “nonreciprocal translocation.” Here, a segment of one chromosome is removed and inserted within another chromosome (in contradistinction to the usual translocation, in which the translocated segment is attached to the end of a recipient chromosome). It is, essentially, a one-way translocation; that is, there is no reciprocal movement back to the originating chromosome. Insertions are rare rearrangements, at the level of detection according to classical cytogenetics. Insertions have their own specific qualities that influence risk assessment, and these are discussed in this chapter.