Sister chromatid exchange and cell cycle in fibroblasts of Bloom's syndrome.

Sister chromatid exchange (SCE) has been studied in the fibroblasts of five Bloom's syndrome patients, one heterozygote, and two normal individuals. The high frequency of SCE already known in the lymphocytes of Bloom's syndrome was also found in the fibroblasts of all five patients. However, populations with low and high frequency of SCE were not found. In addition, chromosome aberrations appeared with a lower frequency. The cell cycle duration in the Bloom's fibroblasts appeared to be similar to that in the normal cell line, and the difference in the growth pattern appeared to be due to the variation in the mitotic index. The cell cycle lasted about 24 h in at least four of the Bloom's lines studied during the present experiments.