When ionizing radiation causes DNA damage (mutations) in male or female reproductive (“germ”) cells, that damage can be transmitted to the next generation (F1). This is in contrast to mutations in somatic cells, which are not transmitted.

Detection of human germ cell mutations is difficult, especially at low doses. While high doses in experimental animals can cause various disorders in offspring (birth defects, chromosome aberrations, etc.), no evidence of clinical or subclinical effects has yet been seen in children of A-bomb survivors. Given the relatively low average dose to survivors (median doses of about 0.14 Gy for both the fathers and mothers), this result is not surprising. It is consistent, in fact, with the predictions of mouse experiments and suggests that humans are not more radiosensitive with respect to heritable changes.

The Table lists the several kinds of genetics studies conducted at ABCC-RERF since the late 1940s in children of A-bomb survivors. Active studies involve ongoing mortality follow-up of the F1 cohort, an F1 clinical examination program, and various molecular studies of DNA from cells of survivors and their children.

Table. ABCC-RERF genetic studies of children of A-bomb survivors

For more-detailed explanations of specific topics related to genetic effects, select a topic below.