Chromosome Aberrations arising spontaneously and induced in Meiotic Cells at Low Levels of Radiation in Tradescantia

IT is of interest in this age of radiation hazards to understand more fully the various parameters of mutation and to partition the mutations induced at low levels of radiation from the frequency arising spontaneously. The work recorded here was initiated for this latter purpose and for the following additional reasons: (1) To establish a reliable and quantitative biological system to detect genetic effects at low doses approaching or less than 1 r. (2) Tradescantia was selected as the test organism because its sensitivity is similar to that of human chromosomes 1,2 . Also Tradescantia has been examined extensively from a radiobiological and biophysical point of view 3,4 . (3) Spontaneous chromosome breakage, which occurs during meiosis, has been examined under a variety of physiological conditions in Tradescantia 5,6 . The progeny of these cultures were examined for spontaneous chromosome mutations and the analysis is presented here. (4) Cells irradiated in meiosis were considered most significant to examine from a genetic point of view since the human female ‘stores’ immature ova at meiotic prophase stages, a state of meiotic arrest established in fœtal development 7 and maintained throughout reproductive life. Meiotic prophase is known to be the most sensitive stage to radiation during the life-cycle in plants and animals 8 .