Intragenic somatic recombination in the Lozenge cistron of Drosophila

Summary

In Drosophila melanogaster intragenic mitotic recombination between the two lozenge alleles, lz ³⁶ and lz ^y4, separated from each other by 0.14 meiotic recombination units, was observed. Among 48 725 females of the genotype w ⁺lz³⁶/w lz^y4 which had been irradiated by a dose of 1000 r X-rays as larvae 41–47 hours after oviposition, a total of 11 faceted eye spots (not lz) were induced. All 11 spots were w ⁺, none w. Possible reasons for the lack of the expected w, faceted spots were checked. Inversion of the X chromosome which would suppress recombination between the w and lz loci was not involved. Gene order of lz ³⁶-lz^y4-kinetochore was confirmed by meiotic recombination test. Nonautonomy of lz gene action was not a factor, as tested by gynanders which showed that lz ^y4 and lz ^s were autonomous. Possibility of reverse mutation was not likely as shown by the large scale control experiments. Gene conversion is suggested as a likely mechanism for the lack of the expected w, faceted spots although the possibility of unequal crossing over induced by X-rays can not be excluded, nor can the preferential z-segregation hypothesis.