The fragile sites was induced to express

in PHA-stimulated lymphocytes chromosome of leukemic patients by low concentrations of folic acid and thymidine in 199 medium. 12 patients and 9 normal controls were examined. The results showed that both rates of the freguencies of fragile sites and the chromosome aberrations in patients were much higher than those in normal controls (20.42% :3.30%). There was significant correlation between the two groups.We found that there are 57 Fra in chromosome. These patients carried 7 of 57 Fra

which were located at the bands of oncogenes loci and cancer breakpoints

these 7 Fra are Ip36(src2)

3p24(rafl)(raf2)

6p23 (krasip)

8q22(mos)

14q24(fos)

22qll(bcr)

22.ql3 (sis). This observation suggests that the fragile sites may associate with leukemia