Genetic variability ofChlamydomonas reinhardtii induced by six urea derivatives

The lethal and mutagenic effect of six urea derivatives applied to the cells of Chlamydomonas reinhardtii Dang was investigated. The mutagenic effect of two N-alkylnitroso derivatives (N-methyl-N-nitroso- and N-ethyl-N-nitrosourea), two monoalkyl derivatives (N-methyl- and N-ethylurea) and two dialkyl derivatives (N,N'-dimethyl- and N,N'-diethylurea) was compared at equal molar concentrations and different cell survival or at equitoxic concentrations, i.e. at equal survival. The former type of appraisal shows the alkylnitroso derivatives to be strong mutagenic agents, exceeding in their effect several times both monoalkyl- and dialkyl derivatives. MNU is seen to be a stronger mutagen than ENU. Alkyl derivatives are generally weak mutagens, the strongest being DEU and the least potent DMU. On using the latter type of evaluation MNU is seen to be clearly the strongest mutagen while the other five compounds, including ENU, have, at equitoxic concentrations, approximately the same effect.