[Radiosensitivity of chromosomes in lymphocytes from Down's syndrome patients].

A study was made of the yield of chromosome aberrations in gamma-irradiated G0 peripheral blood lymphocytes from 6 patients with different forms of Down's syndrome. The doses used were from 0.25 to 3.0 Gy. Seven healthy donors of different age made the control group. There was a significant increase in the yield of chromosome exchanges in lymphocytes from all the patients as compared to control. The spontaneous level of chromosome aberrations and the frequency of radiation-induced fragments did not differ from the control values. The yield of exchanges in diploid and trisomic cells from patients with the mosaic form of Down's syndrome did not change significantly as the time of cultivation was raised. The origin of DNA repair defects leading to the increased chromosome radiosensitivity in Down's syndrome is discussed.