Bone marrow chromosomes are known to be highly radiosensitive. The current study seeks to examine the changes in chromosomal morphology post exposure to gamma radiation in Swiss albino mice. Observation of slides of control mice show no significant damage in chromosomes number (40) and morphology. However, after administration 0.20 Gy, 0.40 Gy, 0.60 Gy, 0.80 Gy of 60 CO-gamma rays a number of abnormalities were observed. Chromosome fragments, breaks, appearance of rings, dicentric chromosomes were found in all cases. The only difference was in their frequency. When the doses were higher the variations were observed more frequently. However, at a dose of 0.60Gy and 0.80 Gy in addition to the aforesaid abnormalities, aneuploidy was also observed. Bone marrow cells showing such defective morphology possibly may also suffer from attenuation of their genetic, physiological and biochemical mechanism(s). These observations indicate the sensitivity of the genomic apparatus of mice subjected to low doses of gamma radiations. The biomedical importance of this study can be easily visualized in the possible cytogenetic effects that would influence the generations to come. The rampant use of this radiation therefore warrants further, indepth investigation in view of the long term genetic hazards and impairment of fertility of an individual due to gamma rays.