The incidence of sister chromatid exchanges in cultured human lymphocytes

The incidence of sister chromatid exchanges (SCE) in cultured human lymphocytes from 50 normal individuals was studied using the BUdR-Giemsa technique. The mean SCE frequency per metaphase was 7.9 with a standard deviation of 1.36 and a range of 1-21. The incidence of exchanges was not influenced by the age of the donor nor did the exchange rate differ between sexes. The results of this study are compared with those of previous reports and reasons for the wide variation between results discussed.