[Sister chromatid exchanges in human lymphocytes in extreme old age].

After the treatment with 5-bromodeoxyuridine (BrdU), the frequency of sister chromatid exchanges (SCE) in the lymphocyte culture cells of peripheric blood tends to be lower in very aged persons, from 80 to 88 years (7.69 +/- 0.34), than in middle aged ones (8.40 +/- 0.33). The reliable decrease in SCE level was assessed in chromosomes A1 and C from the old group persons as compared with the appropriate values in the middle age group. The level of SCE falls in telomeric and centromere regions of chromosomes A1 and A2.