The fate of X-ray-induced chromosome aberrations in blood lymphocyte culture.

The BrdU-Giemsa method which facilitates an unequivocal identification of metaphases at different cycles has been utilized to investigate the fate of X-ray-induced chromosome aberrations in the blood lymphocyte culture system of the Indian muntjac which has the lowest diploid number (2n = 6 female/7 male) and easily distinguishable large-sized chromosomes. The results demonstrate that about 50% of dicentrics and only 12% of rings were transmitted from the first cycle to the second. There were as high as 73% abnormal cells in the second cycle as against 94% in the first cycle following 4.0 Gy. However, the frequencies of dicentrics, rings and of abnormal cells were greatly reduced in the third+ cycles. The frequencies of acentric fragments per post-irradiated first, second and third+ division cell were 2.21, 0.64 and 0.24, respectively. In sharp contrast to all earlier reports, about 75% of them were retained as a single acentric fragment in the second cycle. Analysis of fragment segregation during anaphase separation supports this finding. The survival probability of dicentrics and rings was found to be more than 60% in the second and only 18% in the third+ cycle.