Fragile sites and chromosome breakpoints in constitutional rearrangements I. Amniocentesis.

Since fragile sites may conceivably predispose to chromosome breakage and rearrangements in meiosis, we examined the locations of 278 breakpoints leading to chromosome rearrangements detected in amniocenteses. Of the 278 breakpoints, 59 (21%) were observed to be in bands containing fragile sites compared to an expectation of 31 (11%), a highly significant difference (P less than 0.001). The tendency for breakpoints to be in bands with fragile sites was independent of origin of the rearrangement or class of fragile site, consistent with the concept that fragile sites predispose to heritable chromosome rearrangements.