Long-term biological irradiation experiments require considerable materials and time until to obtain analytical results. Thus, if the results that might be obtained can be predicted when designing an experiment, that information is very useful to those who will perform the experiment. However, there has not been any simulator that can accurately predict such results. This was due to the inadequacy of the mathematical model used for the prediction. Therefore, we have newly created a genetic effect prediction simulator “WAMSIM” based on the calculation principle of a mathematical model “WAM (Whack-A-Mole) model” that can show the variation of genetic effects in a dose rate-dependent manner. Since the WAM model includes the time component as a parameter, it is possible to estimate the fluctuation of the genetic effect even in experimental conditions in which the dose rate changes over time and/or in fractionated irradiation. In this report, we have actually used WAMSIM to predict the effects on the next generation in mice that have been continuously irradiated with low LET radiation for a long period of time or in mice that have received fractionated irradiation. As a result, we have obtained some important findings to keep in mind when conducting irradiation experiments.