Distribution of break points in human structural rearrangements.

We attempted to resolve the issue on the location of breakages in patients with structural rearrangements, that is, whether they are located within the light band or are at the interface between a G-dark and a G-light band. Three types of structural rearrangements (inverted duplications, isodicentrics, and rings) were studied as they are capable of providing information not obtainable from other rearrangements because of reasons given in the RATIONALE. We found that break points are primarily located within the G-light bands; a small number of breaks are located in G-dark bands. Breakages at the interface were exceedingly rare. The possibility that they are, in fact, located at the interface of subbands within either light or dark bands appears tenuous. Contrary to what is described in the literature, terminal deletions are not useful in the determining of break points.