The question of threshold doses for radiation damage: malformations induced by radiation exposure of unicellular or multicellular preimplantation stages of the mouse.

Mouse embryos of the one-cell stage or the 32- to 64-cell stage were exposed to various X-ray doses (one-cell stage: 0.25-2 Gy; 32- to 64-cell stage: 1-3 Gy). It turned out that the shape of the dose-response curves is statistically compatible with the assumption derived from biological considerations that there is no threshold for radiation-induced malformations in the case of the exposure of one-cell embryos, whereas there is a threshold dose (close to 1 Gy) in the case of the exposure of 32- to 64-cell embryos.