Simple chromosome exchanges are not linear with dose

Purpose: To check whether simple chromosome exchanges are linearly related to radiation dose. Materials and methods: Go-irradiated lymphocytes were cultured to produce metaphase preparations. Chromosomes 1 and 2 were painted different colours and the remaining chromosomes counterstained. Cells containing a colour junction involving both chromosomes 1 and 2 were scored fully, so that simple and complex rearrangements were distinguished. Results: At doses of 2Gy and below very few complex rearrangements were seen. About 90% of exchanges were simple. At these doses the linear component of the dose-effect curve accounts on average for only ~30% of the observed yield. Conclusions: There is a square-law dose component to the yield of simple exchanges in addition to the linear term.