LACK OF EFFECTS OF ATOMIC-BOMB RADIATION ON GENETIC INSTABILITY OF TANDEM-REPETITIVE ELEMENTS IN HUMAN GERM-CELLS

In a pilot study to detect the potential effects of atomic bomb radiat ion on germ-line instability, we screened 64 children from 50 exposed families and 60 from 50 control families for mutations at six minisate llite loci by using Southern blot analysis with Pc-1, lambda TM-18, Ch dTC-15, p lambda g3, lambda MS-1, and CEB-1 probes. In the exposed fam ilies, one or both parents received a radiation dose >0.01 Sv. Among t he 64 children, only one child had parents who were both exposed. Thus , of a total of 128 gametes that produced the 64 children, 65 gametes were derived from exposed parents and 63 were from unexposed parents, the latter being included in a group of 183 unexposed gametes used for calculating mutation rates. The average parental gonadal dose for the 65 gametes was 1.9 Sv. We detected a total of 28 mutations at the p l ambda g3, lambda MS-1, and CEB-1 loci, but no mutations at the Pc-1, l ambda TM-18, and ChdTC-15 loci. We detected 6 mutations in 390 alleles of the 65 exposed gametes and 22 mutations in 1098 alleles of the 183 gametes from the unexposed parents. The mean mutation rate per locus per gamete in these six minisatellite loci was 1.5% in the exposed par ents and 2.0% in the unexposed parents. We observed no significant dif ference in mutation rates in the children of the exposed and the unexp osed parents (P = .37, Fisher's exact probability test).