In this research the effects of two different food additives like Mono Sodium Glutamate (MSG) and ribonucleotides [inosine 5'-monophosphate (IMP) and Guanosine 5'-monophosphate (GMP)] have been used for determining the genotoxic potential by the meaning of mitotic index analysis. Allium cepa L. root tip test were used for mitotic index measuring. For comparing the effects of three different concentrations of MSG and ribonucleotides (I+G) after 24, 48 and 72 hours exposure time on A. cepa, root tip test were realized. All experiments were carried out under controlled conditions in the laboratory. According to our research results, it seems that different concentrations MSG and ribonucleotides (I+G) applications has been decreased the mitotic index values in A. cepa depending to increased concentrations and 72 hours exposure time respectively in MSG and ribonucleotides (I+G) as %85.43 and %90.78 when compared with the control group. Research results consistently showed that mitotic cell division has been inhibited with different concentrations of MSG and ribonucleotides (I+G) applications depending to the exposure time.