Based upon animal experimentation, the following generalizations may be made regarding genetic effects from exposure to ionizing radiation: 1. genetic mutational damage is more severe if a given radiation dose is fractionated over a period of years or decades 2. there is no indication of a threshold dose below which genetic damage does not occur 3. the degree of mutational damage seems to be dose-dependent

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

Answer: (C)

In radiation genetics, heritable mutations show a dose–response with no evidence of a safe lower limit. This means even small doses can induce mutations, and the total mutational burden tends to increase as the dose increases. The idea that spreading a fixed dose out over years or decades would make genetic mutational damage more severe isn’t supported by animal data; germline mutations relate more to the total dose delivered, and repair processes affecting somatic tissue don’t translate to a greater heritable effect in the same way. Because of that, the generalizations that hold are that there is no threshold and that the degree of mutational damage is dose-dependent.