Radiobiology > Stochastic Effects > Heritable Effects (cont.)

Heritable Effects, continued

Why are observational data from human populations lacking?

  • The spontaneous mutation rate of the human population is high enough to limit sensitivity for superimposed small increases in risk
  • Most mutations are recessive traits, thus have a low likelihood of expression
  • The mutations produced by ionizing radiations are identical to those expressed from the pre-existing genetic burden or those induced by other mutagens

At low doses, gene mutations are demonstrated in the progeny of irradiated mice. Most of the mutations seen in mice are recessive and deleterious. 

Recall that genetic risk from gonadal irradiation is not equal for both sexes: testes are about two-fold more radiosensitive than female ovaries. Males reach sterility at lower dosages of radiation than do females.

Delay between gonadal irradiation and conception reduced the number of mutations observed in the offspring of mice. From these data, recommendations have been developed for patients whose radiologic exam will contain the gonads or when gonads will likely receive significant exposure from scatter:

  • Females: Allow at least 3 ovulatory cycles before electing to become pregnant
  • Males: Allow at least 2 cell renewal times (approximately 130 days) before attempting to start a family.

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