Cytological effects of three alkylating agents in Drosophila

Three alkylating agents EMS, MMS and (perhaps, for the first time) DPA have been fed to the Drosophila larvae to investigate their effects on salivary chromosomes. Heterozygous paracentric inversions are almost the only type of re-arrangement observed; hence their frequency has been considered to make certain comparisons. The relative efficiency in producing inversions indicates their reactivity in the order DPA>EMS>MMS in Drosophila. There is greater efficiency of difunctional agents over monofunctional agents; and ethylation over methylation. Armwise preference of these chemicals and different segments of salivary chromosome complement repeatedly selected for such action have been pointed out. Besides, EMS, MMS and DPA have shown similarity in affecting a few loci in common. Induction of aberrations is discussed in relation to presence of intercalary-hetero-chromatin.