Question

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:

A. The increased incidence of cancers in the parents is merely coincidental.
B. The study should have examined more genes for mutations.
C. The mutations in the parents were mostly somatic.
D. The mutations in the parents were germ-line only.
E. All of the above.

Answer 1

The single mutation found among children of exposed parents in Nagasaki suggests that transmission of mutations was not significant and that the mutations in the parents were predominantly somatic, not germ-line. These findings align with the fact that high-dose radiation increases cancer risk, but do not support a strong correlation between low-level radiation exposure and inheritable genetic defects.

Step-by-step explanation:

In the study of children of parents exposed to the Nagasaki atomic blast, the data that revealed only one mutation among 289,868 genes analyzed suggests that the mutations observed in the parents were not transmitted to the offspring as germ-line mutations but were more likely somatic mutations. This is consistent with the increased incidence of leukemia and other types of cancers in the exposed parents, showing that while radiation greatly affects cells that divide rapidly (like those in cancers), this does not directly translate into a higher risk of inheritable genetic defects. Animal studies indicate a linear relationship between radiation and genetic defects, but human studies, such as those of survivors from Hiroshima and Nagasaki, do not support this for low to moderate exposures. Hence, the most suitable answer to the presented question is: C. The mutations in the parents were mostly somatic.

The linear hypothesis in radiation safety suggests that any dose of radiation poses a risk to health, however, the actual effects of low-level radiation exposure are a matter of debate, with some researchers arguing for the hormesis effect, where low doses might have beneficial biological responses. Studies on Russian nuclear workers and survivors of other radiation exposures have shown links to various cancers, supporting the view that high doses of radiation can lead to increased cancer risk.