[Somatic mosaicism frequency in the combined action of ethyleneimine and formaldehyde on Drosophila larvae].

The frequencies of somatic mosiacs has been analysed among heterozygotic (w+/w) females, which were treated by ethylene imine (EI) and formaldehyde (F) upon larvae (at the age of 20--24 hours from the moment of eggs laying). It has been shown that EI is much more effective than F in the induction of mosaics. Formaldehyde blocks the development of the larvae at the first age and, influencing either before or after EI, decreases the efficiency of the latter in the induction of somatic mosaics. Similar results (the decrease of the frequency of the EI induced mosaics) is observed in the case when larvae are placed on the non-yeast raisin-sugar medium after the EI treatment for their further development. The data are discussed with respect to repair processes in imaginal disc cells which are more efficient after proliferation blocks in both cases.