Breakpoint distribution in constitutional chromosome rearrangements with respect to fragile sites

Summary In an attempt to investigate possible relationships between fragile site bands and chromosome abnormalities, we have analysed the distribution of 6391 breakpoints found in constitutional rearrangements. Were relative band lengths to be ignored, a general trend for breaks to be located in fragile site bands would be confirmed. On the other hand, no difference was detected between bands with or without fragile sites if the probability of breakage for each single band is assumed to be proportional to its length. Nevertheless, a number of bands with a great excess of breakage events were identified.