Inversions

Inversions are intrachromosomal structural rearrangements. The most common is the simple (or single) inversion. If the inversion coexists with another rearrangement in the same chromosome, it is a complex inversion. In an inversion, a segment of chromosome is switched 180 degrees. If this segment includes the centromere, this is a pericentric inversion; if not, it is a paracentric inversion. In principle, and almost always in practice, it is only the pericentric inversion that conveys an important genetic risk to carriers of the inversion: Their children may inherit a “recombinant” chromosome that would inevitably be imbalanced. This chapter considers these two type of inversions and discusses the degree of genetic risk that may—or may not—be associated.