Nonrandom Distribution of Chromosome Breaks in Lymphocytes of Atomic Bomb Survivors

Abstract

The distribution of breakpoints within chromosomes in lymphocytes of 39 healthy atomic bomb survivors who were heavily exposed were studied by means of G and Q-banding techniques. A total of 1, 414 breakpoints in 651 cells with structural chromosome aberrations were used for the present analyses. The results obtained were as follows: (1) In chromosomes #15, #18 and #22, the breaks were more frequently observed than expected. On the contrary, the number of breaks among chromosomes #1, #2 and X was less than expected. (2) A higher incidence of breakpoints according to the length of regions in 4q3, 5q3 and 14q3 and a lower incidence in regions around centromeres of large chromosomes were observed. (3) Distribution of breakpoints was 26.6% in the centromeric region, 30.8% in the middle region and 42.6% in the telomeric region. (4) Seventy-four percent of the breaks was observed in the negative bands. The present results clearly show that breakpoints in atomic bomb survivors were not randomly distributed interchromosomally as well as intrachromosomally. Detailed chromosome analyses have elucidated the biological significance of chromosome aberrations particularly in relation to the late effects among atomic bomb survivors.