Inversion Chromosomes

A number of findings revealed that chromosome inversions are more frequent than deduced from classical cytogenetic studies. Indeed, some paracentric cryptic inversions have been found to be flanked by segmental duplications, either causing a Mendelian disease owing to the interruption of specific genes at inversion breakpoints or being present in the normal population as a polymorphism. In the latter case, in the heterozygous state they predispose to further unbalanced rearrangements such as inv dup rearrangements or simple deletions and duplications. The importance of this susceptibility factor has been well clarified with respect to some genomic disorders involving chromosome 8p and it is now emerging as a possible model that may explain the genetic basis of other recurrent chromosome rearrangements.