Blood samples were collected from 19,000 children of people who were within 2000 meters of the atomic blast in Nagasaki, Japan. Amino acid substitutions were investigated in 28 proteins and any variants detected led to an analysis of the child's parents' blood proteins to determine if the variant was an inherited or new mutation. Of the 289,868 genes examined, only one mutation was found in the children of parents exposed to the blast. None were found in the control group. This surprised the researchers, as animal studies clearly show that radiation causes mutations. In addition, the exposed parents did exhibit an increased incidence of leukemia and other types of cancers relative to unexposed people. These data suggest that .