The genetically significant dose is dependent upon which of the following factors?

• A. 1 and 2
• B. 1 and 3
• C. 2 and 3
• D. 1, 2, and 3

Answer: (D)

The genetically significant dose reflects the potential genetic impact of radiation on future generations by combining three elements. It depends on the average dose received by the gonads because only germ cell exposure can cause heritable changes. It also depends on how many offspring the population has, since more births mean more opportunities for any new mutations to be passed on. Finally, it depends on the mutation rate per unit dose for germ cells, which determines how likely a given dose will produce genetic changes. Because all three factors—gonadal dose, reproductive rate, and mutation rate per unit dose—influence the expected number of heritable mutations, the genetically significant dose is determined by all of them.