Diepoxybutane-induced male-transmissible X-autosome translocations in Drosophila melanogaster: a test of the supporting evidence for the Lifschytz-Lindsley model of spermatogenesis.

The Lifschytz-Lindley model of spermatogenesis in heterogametic animals postulates a stage of gene inactivation during spermatogenesis, which affects the X-chromosome and the autosomes at different times. The frequent male infertility of X-ray induced X-autosome translocations is attributed to disruption in the timing of this stage by breaks that occur in the interior euchromatic portion of the X. Indeed, all male-fertile X-ray induced translocations between the X and an autosome had their breakpoints in the proximal or distal portion of the X. We now show that this was true also for 16 male-fertile X-autosome translocations that had been induced by an alkylating agent, diepoxybutane (DEB). The significantly higher proportion of male-fertile X-translocations in this experiment than in experiments with ionizing radiation apparently is due to a preference of diepoxybutane for the induction of breaks in the "permissive" regions of the X. Older data suggest that this preference is even stronger for mustard gas as chromosome-breaking agent. While these data do not add further evidence to the Lifschytz-Lindley model, they remove a potential objection to it.