Relative biological effectiveness of x-rays and fast neutrons in inducing translocations in mouse spermatogonia

The dose-response relationships for inducing translocations in the spermatogonia of mice were studied, and they were compared for 200 kVp X-rays and 2 MeV fast neutrons. The dose response for fast neutrons was markedly convex; more precisely, the response obtained was linear in the dose range from 24 to 94 rad with a regression coefficient of 11.36·10^?4, but decreased for a further increase in dose up to 267 rad. On the other hand, that for X-rays showed a linear dose-response relationship from 48 to 672 rad with a regression coefficient of 2.69·10^?4. The relative biological effectiveness for inducing translocations in the spermatogonia of mice was compared for the linear parts of the dose response in both types of radiation, and the relative biological effectiveness (RBE) value was 4.22.