Do one-hit chromosome exchanges exist? Dose-response relation for irradiated human lymphocytes.

It is demonstrated that the expectation of a quadratic dose-response relation for two-hit aberrations is not correct. In fact the theoretical curve is changed from near-quadratic to near-linear when the dose increases and fits well the experimental data on production of exchanges in human lymphocytes by radiation. The commonly used relation y = alphaD + betaD2 shows systematic deviations from the observed frequencies. Therefore, no reason exists to postulate some fraction of exchanges to be produced by a one-hit mechanism.